Communication apparatus and communication method

ABSTRACT

A communication apparatus includes: signal generation circuitry which, in operation, generates a control signal including a target reception power value regarding a target value of a reception power for the communication apparatus to receive an uplink (UL) response frame transmitted by each of one or more terminal stations, the control signal being a trigger frame that solicits transmission of the UL response frame from each of the one or more terminal stations; and transmission circuitry which, in operation, transmits the generated signal.

BACKGROUND 1. Technical Field

The present disclosure relates to a communication apparatus and acommunication method to perform uplink transmission power control.

2. Description of the Related Art

In Task Group ax of the Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 Working Group, a technical specification of IEEE802.11ax (hereinafter, 11ax) is being developed as a next standard thatwould replace 802.11ac. In 11ax, a multi-user transmission method(hereinafter, MU transmission) based on the orthogonalfrequency-division multiple access (OFDMA) and the multi user-multiinput multi output (MU-MIMO) is expected to be introduced to uplink(UL).

In a UL MU transmission procedure, an access point (also called a basestation) transmits a control signal as a trigger for an uplink signal tomultiple stations (also called STAs) within the area covered by theaccess point. Based on the control signal, a station, which transmitsthe uplink signal, transmits an UL response signal (also called a ULresponse frame) to the access point. There are two methods for the UL MUtransmission procedure: one in which an access point specificallydesignates a station and allocates a frequency resource (hereinafter, aresource unit (RU)) thereto; and the other in which a station selectsthe RU by a random access (RA). A trigger frame (TF) is a control signalby which the access point specifically designates a station andindicates a corresponding resource, and a trigger frame-random (TF-R) isa control signal by which the access point indicates at least one randomaccess resource.

The TF-R includes allocation information for a station that secures theresource by the random access (hereinafter, random access allocationinformation) and allocation information for a station specificallydesignated for the resource allocation (hereinafter, specific allocationinformation). A station that transmits the UL response signal by therandom access decodes RU information for the random access from theTF-R, selects one RU randomly from multiple random access RUs, andtransmits the UL response signal using the selected RU (e.g., see IEEE802.11-15/0132R12 “SPECIFICATION FRAMEWORK FOR TGAX”).

SUMMARY

However, in the above-described MU transmission with the random accessinstructed by the random access control signal (TF-R), it is difficultfor the access point side to determine which station secures theresource by the random access. Thus, the access point cannot setappropriate transmission power of the station that transmits the ULresponse signal by the random access. This leads a problem that areception power difference between the stations in the access pointincreases and a reception signal in the access point does not fallwithin the dynamic range of A/D conversion, or a problem that the Signalto Interference plus Noise Ratio (SINR) decreases due to interferencebetween the stations.

One non-limiting and exemplary embodiment provides a communicationmethod and a communication apparatus that can solve carrier interferenceand a problem of the dynamic range of A/D conversion by efficientlyperforming transmission power control in a UL response signaltransmitted through MU transmission by the random access and reducing areception power difference between stations in an access point.

In one general aspect, the techniques disclosed here feature acommunication apparatus according to an aspect of the present disclosureincludes: signal generation circuitry which, in operation, generates acontrol signal including a target reception power value regarding atarget value of a reception power for the communication apparatus toreceive an uplink (UL) response frame transmitted by each of one or moreterminal stations, the control signal being a trigger frame thatsolicits transmission of the UL response frame from each of the one ormore terminal stations; and transmission circuitry which, in operation,transmits the generated signal.

It should be noted that such inclusive or specific aspects may beimplemented as a system, a device, a method, an integrated circuit, acomputer program, or a storage medium, or may be implemented as anyselective combination of a system, a device, a method, an integratedcircuit, a computer program, and a storage medium.

According to an aspect of the present disclosure, the reception powerdifference between the stations in the access point can be reduced inthe UL response signal transmitted through the MU transmission by therandom access, and this can reduce the interference (MU interference)between the station in the MU transmission and can make a receptionsignal fall within the dynamic range of A/D conversion.

Further advantages and effects in an aspect of the present disclosurebecome apparent from the description and the drawings. Those advantagesand/or effects are provided in accordance with the features illustratedin some embodiments as well as the description and the drawings;however, not all of the advantages and the effects are necessarilyprovided to obtain one or more of the same features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart that illustrates operations of an access point anda station according to Embodiment 1;

FIG. 2 is a block diagram that illustrates a main configuration of theaccess point according to Embodiment 1;

FIG. 3 is a block diagram that illustrates a main configuration of thestation according to Embodiment 1;

FIG. 4 is a block diagram that illustrates a configuration of the accesspoint according to Embodiment 1;

FIG. 5 is a block diagram that illustrates a configuration of thestation according to Embodiment 1;

FIG. 6 is a diagram that illustrates an example of a random accesscontrol signal according to a transmission power control information andfield setting method 1 of Embodiment 1;

FIG. 7A is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 1 (specific allocation) in the transmission power controlinformation and field setting method 1 of Embodiment 1;

FIG. 7B is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 2 (specific allocation) in the transmission power controlinformation and field setting method 1 of Embodiment 1;

FIG. 7C is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 3 (specific allocation) in the transmission power controlinformation and field setting method 1 of Embodiment 1;

FIG. 8A is a diagram that illustrates an example of an allowable powerdifference depending on performance of A/D conversion according to thetransmission power control information and field setting method 1 ofEmbodiment 1;

FIG. 8B is a diagram that illustrates an example of an allowable powerdifference depending on the number of multiplex stations according tothe transmission power control information and field setting method 1 ofEmbodiment 1;

FIG. 9A is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 1 (random access allocation) in the transmission power controlinformation and field setting method 1 of Embodiment 1;

FIG. 9B is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 2 (random access allocation) in the transmission power controlinformation and field setting method 1 of Embodiment 1;

FIG. 9C is a diagram that illustrates an example of purposes and targetreception power according to a target reception power setting method 4(random access allocation) in the transmission power control informationand field setting method 1 of Embodiment 1;

FIG. 10 is a diagram that illustrates an example of a random accesscontrol signal according to a transmission power control information andfield setting method 2 of Embodiment 1;

FIG. 11A is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 1′ (specific allocation) in the transmission power controlinformation and field setting method 2 of Embodiment 1;

FIG. 11B is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 2′ (specific allocation) in the transmission power controlinformation and field setting method 2 of Embodiment 1;

FIG. 11C is a diagram that illustrates an example of a target receptionpower determining method according to a target reception power settingmethod 3′ (specific allocation) in the transmission power controlinformation and field setting method 2 of Embodiment 1;

FIG. 12 is a diagram that illustrates an example of a target receptionpower value of each type of a response signal according to atransmission power control information and field setting method 3 ofEmbodiment 1;

FIG. 13 is a diagram that illustrates an example of a target receptionpower value for each allocation method according to a transmission powercontrol information and field setting method 4 of Embodiment 1;

FIG. 14 is a diagram that illustrates an example of a random accesscontrol signal according to a transmission power control information andfield setting method 5 of Embodiment 1;

FIG. 15 is a diagram that illustrates an example of a pattern of atarget reception power offset according to the transmission powercontrol information and field setting method 5 of Embodiment 1;

FIG. 16 is a diagram that illustrates an example of a random accesscontrol signal according to a transmission power control information andfield setting method 6 of Embodiment 1;

FIG. 17 is a diagram that illustrates an example of a random accesscontrol signal according to a transmission power control information andfield setting method 7 of Embodiment 1;

FIG. 18 is a flowchart according to path-loss feedback timing 1 ofEmbodiment 1;

FIG. 19 is a flowchart according to path-loss feedback timing 2 ofEmbodiment 1;

FIG. 20 is a flowchart according to path-loss feedback timing 3 ofEmbodiment 1;

FIG. 21 is a flowchart according to path-loss feedback timing 4 ofEmbodiment 1;

FIG. 22 is a block diagram that illustrates a configuration of a stationaccording to Embodiment 2;

FIG. 23 is a diagram that illustrates an example that transmission isstopped or not depending on a type of a response signal according to adetermining method 6 of Embodiment 2;

FIG. 24 is a block diagram that illustrates a main configuration of anaccess point according to Embodiment 3;

FIG. 25 is a diagram that illustrates an example of a UL MU transmissionprocedure in a controlling method 1 of Embodiment 3;

FIG. 26A is a diagram that illustrates an example of an allowancecondition in an allowance condition setting method 1 of Embodiment 4;

FIG. 26B is a diagram that illustrates an example of an allowancecondition in an allowance condition setting method 2 of Embodiment 4;

FIG. 26C is a diagram that illustrates an example of an allowancecondition in an allowance condition setting method 3 of Embodiment 4;

FIG. 27A is a diagram that illustrates an example of a range of anallowable power value in a range of allowable power value setting method1 of Embodiment 4;

FIG. 27B is a diagram that illustrates an example of a range of anallowable power value in a range of allowable power value setting method2 of Embodiment 4;

FIG. 27C is a diagram that illustrates an example of a range of anallowable power value in a range of allowable power value setting method3 of Embodiment 4; and

FIG. 27D is a diagram that illustrates an example of a range of anallowable power value in a range of allowable power value setting method4 of Embodiment 4.

DETAILED DESCRIPTION Underlying Knowledge Forming Basis of the PresentDisclosure

Each of the TF and the TF-R includes Common information field (alsocalled Common field and hereinafter called a “common field”) fornotifying a station to which an MU transmission resource is allocated ofcommon control information and User information field (also called anSTA-specific field or an RU-specific field, and hereinafter called a“station-specific field”) for notifying every station or every RU ofspecific control information. The common field includes Trigger type fornotifying of a type of TF, and so on. Meanwhile, the station-specificfield includes information for identifying a station (e.g., AssociationID (AID)), Modulation and Coding Scheme (MCS), and so on (e.g., see IEEE802.11-15/0132R12 “SPECIFICATION FRAMEWORK FOR TGAX”).

In addition, multiple TFs and TF-Rs can be successively transmitted in atransmission opportunity (TXOP) (also called multiple trigger frame in aTXOP). Whether the successive transmission of the TFs and the TF-Rsoccurs can be indicated in a cascade field (also called cascaded field)in each of the TFs and the TF-Rs (e.g., see IEEE 802.11-15/0132R12“SPECIFICATION FRAMEWORK FOR TGAX”).

Since the UL MU transmission has carrier interference and the problem ofthe dynamic range of AD conversion due to a reception power differencebetween the stations in the access point, the necessity of transmissionpower control of each station has been discussed (e.g., see IEEE802.11-14/1446R0 “ANALYSIS OF FREQUENCY AND POWER REQUIREMENTS FORUL-OFDMA”).

However, as for uplink transmission power control, although 802.11hdefines a format such as the TPC report/request, there is no definitionof a specific controlling method. The TPC report is included in abeacon, a probe response, or an action frame. In the TPC report,notification of transmission power (Equivalent Isotopic Radiation Power(EIRP)) and a link margin are provided. The link margin is controlinformation only for notifying of an excessive quality, and a stationreceiving the link margin can reduce the transmission power by the linkmargin (e.g., see IEEE STD 802.11H-2003).

As described above, the link margin in the transmission power controlaccording to 802.11h is only for notifying of the excessive quality, andthus no control for increasing the transmission power can be performed.Hence, the transmission power control according to 802.11h cannot beapplied as the transmission power control to solve the above problems inthe UL MU transmission.

In addition, in the long term evolution (LTE) random access,notification of a target reception power value common for cells andpower ramping are provided using radio resource control (RRC) signaling,and the station performs control for increasing the transmission powerby the power ramping at every retransmission based on the initial targetreception power. The target reception power can be semi-staticallychanged at intervals of at least 640 ms (e.g., see 3GPP TS 36.331).

As described above, since the cycle for changing the target receptionpower value is long in the LTE transmission power controlling method,the target reception power value cannot be changed at every schedulingdepending on a combination of the stations to which the resources areallocated. That is, when the LTE transmission power control is appliedin the UL MU transmission, it is still possible to perform control suchas fixing the target reception power value of a station positioned at acell edge (hereinafter called a cell edge station), but it is impossibleto dynamically control the target reception power value to fit that withrespective qualities of a station near the access point and the celledge station far from the access point. Thus, scheduling gain, or gainmade by the optimum adaptation modulation performed on every stationbased on a reception quality of each station in the access point cannotbe obtained.

Thus, an object of an aspect of the present disclosure is to efficientlyperform the transmission power control in the UL MU transmission.Specifically, the object is to solve the carrier interference and theproblem of the dynamic range of A/D conversion by introducing efficienttransmission power control to the UL response signal, which istransmitted through the MU transmission by the random access to theresource indicated by the random access control signal, and reducing thereception power difference between the stations in the access point. Inaddition, the object is to improve the system throughput by dynamicallychanging the target reception power value at every scheduling dependingon the reception qualities of the random access-allocation station andthe specific-allocation station and making possible immediateapplication of the optimum adaptation modulation of every station.

Embodiments of the present disclosure are described below in detailswith reference to the drawings. Note that, in the embodiments, the sameconstituents are denoted by the same reference numerals to avoidduplicated description thereof.

Embodiment 1 Summary of Communication System

A communication system according to this embodiment includes an accesspoint (communication apparatus) 100 and a station 200. The access point100 is an access point applicable to 11ax, and the station 200 is astation applicable to 11ax.

FIG. 1 illustrates a sequence of processing in the communication systemaccording to this embodiment.

In FIG. 1 , the access point 100 generates a beacon signal (step(hereinafter, represented as “ST”) 101).

The beacon signal includes transmission power of the access point 100.Specifically, equivalent isotropic radiated power (hereinafter, EIRP) ofthe access point 100 is set as the transmission power. In general, theEIRP is broadcast determined based on antenna gain in the maximumradiated direction of a directional antenna. Thus, when the station 200performs later-described path-loss estimation and transmission powersetting based on the EIRP, a difference may occur between actualreception power and target reception power in the access point. In orderto solve this problem, total radiated power (hereinafter, TRP) of theaccess point 100 may be used as the broadcast transmission power. Usingthe TRP when applying beam forming can reduce the difference in thereception power due to a position of the station 200 and a difference ina direction of the beam. The transmission power may be broadcast to thestations 200 using a management frame such as Probe Response andAssociation Response, or may be broadcast to the station 200 while beingincluded in the random access control signal.

The access point 100 notifies the station 200 of the reception power thegenerated beacon signal is wirelessly provided to (ST102).

The access point 100 performs scheduling (frequency allocation, MCSselection) of downlink data (DL data)/UL response signal (ST103). Theaccess point 100 may perform the scheduling using channel stateinformation (CSI), which is provided as feedback from the station 200.

Based on the scheduling result, the access point 100 sets a targetreception power value of each station to which the resource is allocated(ST104). A method of setting the target reception power value isdescribed later.

The access point 100 generates a random access (RA) control signal(TF-R) (ST105).

The random access control signal includes at least one piece of randomaccess allocation information and may optionally include specificallocation information. In the specific allocation information, a uniqueID for discrimination of the station 200 (STA_ID) is used to clearlyindicate the allocation of the RU. That is, each station 200 determinesthat the RU to which its own ID is allocated as the RU available fortransmission of the UL response signal. Meanwhile, in the random accessallocation information, a random access ID is used to clearly indicatethe allocation of the random access RU. As the random access ID, an IDthat is not allocated for the discrimination of a specific station 200is used. For example, an association ID (AID), which is a unique ID thatis allocated during association with a network where the access point100 belongs (basic service set (BSS), multiple stations 200 under theaccess point 100), may be used as the STA_ID, and a spare value, whichis not generally used as the AID, may be used as the random access ID.

In this embodiment, the access point 100 puts the target reception powervalue into the random access control signal. The access point 100provides the notification of the target reception power value using therandom access control signal, and thus the target reception power valuecan be dynamically changed at every scheduling depending on thereception qualities of the random access-allocation station or thespecific-allocation station. Thus, the optimum adaptation modulation canbe immediately applied to each station 200, and hence the systemthroughput is improved.

Note that the target reception power value is a power value (targetvalue) as a target of the reception power when the access point 100receives the UL response signal of each station 200. Each station 200controls the transmission power so as to make the reception power of theaccess point 100 fall within a predetermined allowable power difference(±X[dB]) of the target reception power value. The access point 100notifies the station 200 of the allowable power difference using themanagement frame such as the beacon, Probe Response, and AssociationResponse. As the allowable power difference is controlled by themanagement frame, an appropriate value can be set for each basic serviceset ((BSS), multiple stations under the access point). In addition, thenotification of the allowable power difference may be provided using therandom access control signal. Even though the control of the allowablepower difference at every transmission of the random access controlsignal increases overhead, in an environment where a state of thestation 200 greatly changes, appropriate control following the changecan be made. In this case, a range including an upper limit value and alower limit value specified by the allowable power difference of thetarget reception power value can also be called an allowable powerrange.

In addition, the target reception power value may not be necessarily anabsolute value of the reception power and may be an offset value from areference such as the minimum reception quality. Moreover, a magnitudeand the notification bit number of the allowable power difference of thetarget reception power value may be different in the random accessallocation and the specific allocation. If collision occurs in therandom access, the reception power is significantly increased, and thiscauses the power difference. Thus, for example, setting the allowablepower difference small in the random access allocation can lower theupper limit value of the reception power when collision occurs.

The access point 100 wirelessly notifies the station 200 of thegenerated random access control signal (ST106).

With reference to the own station information, the station 200 specifiesan available RU from the RUs indicated by the notification of the randomaccess control signal provided (broadcast) from the access point 100(ST107). Specifically, when there is control information including ownSTA_ID in the station-specific field of the random access controlsignal, the station 200 determines that this is the specific allocation.On the other hand, when there is control information including no ownSTA_ID but the random access ID in the station-specific field andfurther retains a signal to be transmitted by the random access, thestation 200 determines that this is the random access allocation andselects an RU according to a predetermined process.

When the RU is secured, the station 200 estimates path-loss based on thetransmission power, antenna gain, and the like that are provided asnotification by the beacon signal (ST108). The path-loss estimation isexpressed in Equation (1).

pathLoss=ApTxPower+ApTxAntGain−StaRxPower  (1)

In Equation (1), pathLoss is the estimated path-loss [dBm], ApTxPower isthe transmission power (TRP) [dBm] of the access point 100 provided asnotification from the beacon and the like, StaRxPower is the receptionpower (dBm) in an antenna element of preamble or data in the station200, and ApTxAntGain is the antenna gain [dB] of the access point 100.

The antenna gain includes beam forming gain. ApTxAntGain may be providedas notification from the access point 100 to the station 200 using themanagement frame such as the beacon, Probe Response, and AssociationResponse, or, may be calculated based on the number of transmissionantennae of the access point 100 in the station 200. The access point100 preferably provides the notification of ApTxPower and ApTxAntGainusing the same frame, and then the station 200 preferably measures thereception power of that frame. In addition, when measuring the receptionpower of the random access control signal, the station 200 may obtainpower of a sub carrier included in the RU for transmitting the ULresponse signal to convert the obtained power to power for the full bandif necessary. This can reduce an error due to the interference and thefrequency selectivity. Moreover, since the beam forming gain isdifferent depending on the frame or a part (preamble (legacy or highefficiency (HE), data) in which the reception power is measured, thebeam forming gain may be changed depending on the measurement target.Specifically, no beam forming gain may be included when the measurementtarget is a broadcast frame such as the beacon and the random accesscontrol signal, non-HT duplicate PPDU that is backward compatible withthe legacy method, and the legacy preamble of a specific address frame,while the beam forming gain may be included when the measurement targetis remainder behind the HE preamble of a specific address frame. Takinginto consideration the beam forming gain improves the estimationaccuracy of the path-loss when measuring the remainder behind the HEpreamble. Reception power of a signal that is received immediatelybefore or average reception power is used as the reception power.

Note that, when the station 200 estimates the path-loss based on asignal to which no beam forming is applied (e.g., the random accesscontrol signal), ApTxAntGain in Equation (1) may be regarded as the beamforming gain and thus be ignored, and then the following Equation (2)may be used. Even when the station 200 estimates the path-loss based ona signal in which the beam forming is effective, if the transmissionpower ApTxPower is the EIRP, the beam forming gain is included inApTxPower, and thus the following Equation (2) may be used.

pathLoss=ApTxPower−StaRxPower  (2)

The station 200 generates the UL response signal to be transmittedthrough the MU transmission by the random access (e.g., data, a bufferstatus report, or a DL data request signal) (ST 109).

The station 200 sets the transmission power of the UL response signalusing the estimated path-loss and the target reception power included inthe random access control signal (ST110). Note that the path-loss thatis estimated based on a downstream signal (the signal from the accesspoint 100 to the station 200) is applied. That is, because of thereversibility between upstream and downstream propagation paths, thepath-loss of the downstream signal is applied as the path-loss forcalculating the transmission power of the UL response signal (signalfrom the station 200 to the access point 100). The transmission power ofthe UL response signal is calculated based on Equation (3), for example.Note that, when the transmission power is greater than the maximumtransmission power allowed by the station 200, or when the transmissionpower is less than the minimum transmission power allowed by the station200, the station 200 transmits the UL response signal with the maximumtransmission power or the minimum transmission power.

StaTxPower=α·pathLoss+P_(target)+StaTxAntGain+10log₁₀(RUsize)+C  (3)

In Equation (3), StaTxPower is the transmission power (dBm) set by thestation 200, pathLoss is the path-loss [dBm] estimated based on Equation(1) or Equation (2), α is a correction coefficient multiplied by thepath-loss, P_(target) is the target reception power value [dBm] providedas notification by the random access control signal, StaTxAntGain is theantenna gain [dB] of the station 200, and RUsize is a size of theallocated RU. In addition, C is an environment-dependent correctionconstant, which is set depending on a state of surrounding overlappingBSS (OBSS), for example. Note that P_(target) is the reception power inthe antenna element.

The access point 100 may notify the station 200 of the correctioncoefficient α of the path-loss using the management frame such as thebeacon, Probe Response, and Association Response, or, may broadcast thestations 200 of the correction coefficient α of the path-loss whileincluding in the random access control signal. As the correctioncoefficient α is controlled using the management frame, an appropriatevalue can be set for each BSS. In addition, as the correctioncoefficient α is controlled at every transmission of the random accesscontrol signal, even though overhead is increased, in an environmentwhere a state of the station greatly changes, appropriate controlfollowing the change can be made.

The correction coefficient α is set while, for example, considering theinterference in the BSS in the OBSS environment in which multiple BSSsare densely arranged. For example, when the number of the surroundingBSSs is large, the correction coefficient α is set to a small value(e.g., 0.8) to reduce the transmission power of the cell edge station,and thus the interference in the surrounding BSSs is reduced. On theother hand, when the number of the surrounding BSSs is small, thecorrection coefficient α is set to a large value (e.g., 1.0) to increasethe transmission power of the cell edge station, and thus the throughputof the cell edge station is improved.

The station 200 transmits the UL response signal to the access point 100with the set transmission power (ST111).

The sequence of processing in the communication system according to thisembodiment is described above.

FIG. 2 is a block diagram that illustrates a main configuration of theaccess point 100 according to this embodiment. In the access point 100illustrated in FIG. 2 , a transmission power control information settingunit 103 sets the transmission power control information for eachresource based on the target reception power value obtained from atarget reception power setting unit 102 and resource allocationinformation (such as the specific allocation and the random accessallocation) obtained from a scheduling unit 101. An RA control signalgenerating unit 104 generates the random access control signal (TF-R),which includes allocation information indicating at least onetransmission frequency resource. The random access control signalincludes the target reception power value calculated by the transmissionpower control information setting unit 103. The radiotransmitting-receiving unit 106 transmits the random access controlsignal.

FIG. 3 is a block diagram that illustrates a main configuration of thestation 200 according to this embodiment. A radio transmitting-receivingunit 202 receives the random access control signal (TF-R), whichincludes the allocation information indicating at least one transmissionfrequency resource. Here, one of the multiple random access IDs isallocated to each of the one or more transmission frequency resources.An RA control signal decoding unit 204 obtains the target receptionpower value included in the random access control signal. In a path-lossestimating unit 207, the path-loss is estimated based on thetransmission power provided as notification from the access point 100and the reception power of the reception signal. A transmission powercalculating unit 205 sets the transmission power of the response signalusing the target reception power value and the path-loss.

Configuration of Access Point 100

FIG. 4 is a block diagram that illustrates a configuration of the accesspoint 100 according to this embodiment. In FIG. 4 , the access point 100includes the scheduling unit 101, the target reception power settingunit 102, the transmission power control information setting unit 103,the RA control signal generating unit 104, a transmission signalgenerating unit 105, the radio transmitting-receiving unit 106, anantenna 107, a reception signal demodulating unit 108, a feedbackinformation decoding unit 109, and a response signal decoding unit 110.Note that the scheduling unit 101, the target reception power settingunit 102, the transmission power control information setting unit 103,and the RA control signal generating unit 104 constitute an accesscontrol (media access control (MAC)) unit, and the transmission signalgenerating unit 105, the reception signal demodulating unit 108, thefeedback information decoding unit 109, and the response signal decodingunit 110 constitute a base band (BB) processing unit.

Based on the CSI, the buffer status report, and the like that areprovided as feedback from each station 200, the scheduling unit 101determines the RU allocation and the MCS of each station 200. As forthese stations 200, since the access point 100 designates the stations200 to which the resources are allocated, they are the station of thespecific allocation. On the other hand, when the resources are needed tobe allocated to the stations 200 by the random access, the schedulingunit 101 secures the random access RUs.

The target reception power setting unit 102 sets the target receptionpower value of each RU based on a state of the RU allocation of thescheduling unit 101. The target reception power setting unit 102 sets atleast one target reception power value as the UL transmission powercontrol information for controlling upstream transmission power of eachof the multiple stations 200. Details of a method of setting the targetreception power value by the target reception power setting unit 102 aredescribed later.

Based on the target reception power value determined by the targetreception power setting unit 102 and the resource allocation informationindicating the scheduling result determined by the scheduling unit 101,the transmission power control information setting unit 103 generatesthe transmission power control information for each RU. Details of thecontrol information set by the transmission power control informationsetting unit 103 are described later. Note that the scheduling unit 101may start over the scheduling by, for example, reselecting the MCS,based on the transmission power control information calculated by thetransmission power control information setting unit 103.

The RA control signal generating unit 104 generates the random accesscontrol signal for requesting the station 200 to transmit the ULresponse signal. The random access control signal includes the Triggertype, which provides notification of a type of the control signal(common field), the station identification information (station-specificfield), the MCS (station-specific field), and the like. For the stationidentification information, a unique ID for identifying the station 200(STA_ID) is set for the specific allocation, while the random access IDis set for the random access allocation. In addition, the random accesscontrol signal includes the transmission power control information setby the transmission power control information setting unit 103.Moreover, the random access control signal includes at least one targetreception power value. Details of the set transmission power controlinformation and the field (common field or station-specific field) aredescribed later.

The transmission signal generating unit 105 performs encode andmodulation processing on the random access control signal inputted fromthe RA control signal generating unit 104. In addition, the transmissionsignal generating unit 105 performs the encode and modulation processingon the information indicating the transmission power of the access point100 and the information indicating transmission antenna gain of theaccess point 100. The transmission signal generating unit 105 thenapplies to the modulated signal the control signal (also called thepreamble) such as a pilot signal and a channel estimation signal usedfor frequency synchronization and timing synchronization at the receiverside (station 200), generates a radio frame (transmission signal), andoutputs that to the radio transmitting-receiving unit 106.

The radio transmitting-receiving unit 106 performs predetermined radiotransmitting processing such as D/A conversion on the signal inputtedfrom the transmission signal generating unit 105 and up-conversion onthe carrier frequency, and then transmits the radio transmissionprocessed signal via the antenna 107.

When receiving the UL response signal (a signal responding the randomaccess control signal transmitted by the access point 100) and thefeedback information from the station 200, the access point 100 operatesas below.

The radio signal received via the antenna 107 is inputted to the radiotransmitting-receiving unit 106. The radio transmitting-receiving unit106 performs predetermined radio receiving processing such asdown-conversion of the carrier frequency on the radio signal and thenoutputs the radio receiving processed signal to the reception signaldemodulating unit 108.

The reception signal demodulating unit 108 performs autocorrelationprocessing and the like on the signal inputted from the radiotransmitting-receiving unit 106 to extract the received radio frame andthen outputs that to the feedback information decoding unit 109 and theresponse signal decoding unit 110.

The feedback information decoding unit 109 demodulates and decodes thefeedback such as the CSI and the path-loss provided from the station 200in the radio frame inputted from the reception signal demodulating unit108 and then outputs that to the scheduling unit 101.

The response signal decoding unit 110 demodulates and decodes the ULresponse signal included in any one of the RUs indicated by the randomaccess control signal in the radio frame inputted from the receptionsignal demodulating unit 108. The response signal decoding unit 110outputs the reception result to the scheduling unit 101. Based on thereception result, the scheduling unit 101 performs retransmissioncontrol and the like.

Configuration of Station 200

FIG. 5 is a block diagram that illustrates a configuration of thestation 200 according to this embodiment. In FIG. 5 , the station 200includes an antenna 201, the radio transmitting-receiving unit 202, areception signal demodulating unit 203, the RA control signal decodingunit 204, the transmission power calculating unit 205, a power controlinformation accumulating unit 206, the path-loss estimating unit 207, afeedback information generating unit 208, a response signal generatingunit 209, and a transmission signal generating unit 210. In addition,the transmission power calculating unit 205, the power controlinformation accumulating unit 206, the path-loss estimating unit 207,the feedback information generating unit 208, and the response signalgenerating unit 209 constitute an access control unit (MAC), and thereception signal demodulating unit 203, the RA control signal decodingunit 204, and the transmission signal generating unit 210 constitute abase band (BB) processing unit.

The radio transmitting-receiving unit 202 receives the signaltransmitted from the access point 100 (FIG. 4 ) via the antenna 201,performs predetermined radio receiving processing such asdown-conversion and A/D conversion on the reception signal, outputs theradio receiving processed signal to the reception signal demodulatingunit 203, and then outputs the information indicating the receptionpower to the power control information accumulating unit 206. Inaddition, the radio transmitting-receiving unit 202 performspredetermined radio transmitting processing such as D/A conversion andup-conversion of the carrier frequency on the signal inputted from thelater-described transmission signal generating unit 210 and outputs theradio receiving processed signal via the antenna 201.

The reception signal demodulating unit 203 performs autocorrelationprocessing and the like on the signal inputted from the radiotransmitting-receiving unit 202 to extract the received radio frame andthen outputs that to the RA control signal decoding unit 204. Inaddition, the reception signal demodulating unit 203 outputs theinformation indicating the transmission power and the transmissionantenna gain of the access point 100 included in the extracted radioframe to the power control information accumulating unit 206.

The RA control signal decoding unit 204 demodulates and decodes therandom access control signal included in the transmission RU of therandom access control signal in the radio frame inputted from thereception signal demodulating unit 203, outputs the transmission powercontrol information to the transmission power calculating unit 205, andoutputs the information such as the MCS that is required for generatingthe transmission signal, to the transmission signal generating unit 210.

The power control information accumulating unit 206 stores informationindicating the reception power inputted from the radiotransmitting-receiving unit 202 and information indicating thetransmission power and the transmission antenna gain of the access point100 inputted from the reception signal demodulating unit 203.

Based on the transmission power (and also the transmission antenna gainin Equation (1)) of the access point 100 inputted from the power controlinformation accumulating unit 206 and the measured reception power, thepath-loss estimating unit 207 calculates the path-loss using Equation(1) or Equation (2), and outputs that to the transmission powercalculating unit 205 and the feedback information generating unit 208.

Based on the target reception power value included in the transmissionpower control information inputted from the RA control signal decodingunit 204 and the path-loss inputted from the path-loss estimating unit207, the transmission power calculating unit 205, for example,calculates the transmission power of the UL response signal usingEquation (3).

The feedback information generating unit 208 generates, if necessary,estimated channel state information (CSI, RSSI) and feedback informationincluding, for example, the path-loss inputted from the path-lossestimating unit 207 and outputs that to the transmission signalgenerating unit 210. The timing for providing the path-loss as feedbackis described later.

The response signal generating unit 209 generates a station ID of thestation 200 and the UL response signal including the transmissioninformation on the station 200 (such as the data, the buffer statusreport, or the DL data request) and outputs them to the transmissionsignal generating unit 210.

The transmission signal generating unit 210 uses the information such asthe MCS inputted from the RA control signal decoding unit 204 to performencoding and modulating on the UL response signal inputted from theresponse signal generating unit 209 or the feedback information inputtedfrom the feedback information generating unit 208. The transmissionsignal generating unit 210 then applies to the modulated signal thecontrol signal (preamble) such as the pilot signal and the channelestimation signal used for the frequency synchronization and the timingsynchronization at the receiver side (access point 100), generates theradio frame (transmission signal), and outputs that to the radiotransmitting-receiving unit 202.

Transmission Power Control Information and Field Setting Method

Next, the transmission power control information in the above-describedaccess point 100 and the field set to the random access control signalare described in detail.

Hereinafter, transmission power control information and field settingmethods 1 to 7 are described severally.

<Setting Method 1>

In the setting method 1, the access point 100 (RA control signalgenerating unit 104) arranges the target reception power value in thestation-specific field of the random access control signal. FIG. 6illustrates an example of the random access control signal according tothe setting method 1. The Trigger type in FIG. 6 indicates a type of thetrigger frame and, for example, the Trigger type is set to indicate thatthe trigger frame is the random access control signal.

After receiving the random access control signal, the station 200obtains the target reception power value arranged in thestation-specific field to which the STA_ID or the random access ID ofthe station 200 (own device) is set as station identification ID. Then,based on the path-loss calculated by the path-loss estimating unit 207and the above-described obtained target reception power value, thestation 200, for example, calculates the transmission power of theresponse signal using Equation (3) and performs the transmission powercontrol on the response signal.

Target Reception Power Value Setting Method

Next, a method of setting the target reception power value in the accesspoint 100 when the setting method 1 is applied is described. Note thatthe target reception power value is a reception power value in theantenna element. Thus, when determining the target reception power valuebased on the reception power including reception antenna gain, theaccess point 100 needs to modify the determined target reception powervalue to a value from which the reception antenna gain is removed and tonotify the station 200 of the modified value.

Hereinafter, target reception power value setting methods 1 to 3 in thespecific allocation are described severally with reference to FIGS. 7Ato 7C.

<Target Reception Power Setting Method 1 (Specific Allocation)>

With reference to the station information and the MCS of each station200 indicating the resource allocated by the specific allocation, whichare determined by the scheduling unit 101, the target reception powersetting unit 102 determines the target reception power value based onthe difference of the lowest required reception power of each MCSbetween the resources. Note that the lowest required reception power(minimum sensitivity) of each MCS is defined in the 802.11 specification(e.g., see IEEE STD 802.11-2012 for a case of 11n).

FIG. 7A illustrates an example of a method of determining the targetreception power according to the target reception power setting method 1(specific allocation) in the setting method 1. In FIG. 7A, resources(RU=1, 2, 3) are respectively allocated to three stations (ID=1, 2, 3).The MCSs of the respective stations are #2, #3, #5.

The target reception power setting unit 102 adds offsets (offsets 1 to3) to the lowest required reception power of the MCSs respectively andsets the offsets to allow a difference between the maximum and theminimum of the reception power to fall within the allowable powerdifference. For example, in FIG. 7A, among the MCSs #2, #3, and #5, thetarget reception power setting unit 102 sets each offset to allow adifference between the reception power in which the offset 3 is added tothe lowest required reception power of the MCS #5, which has the maximumlowest required reception power, and the reception power in which theoffset 1 is added to the lowest required reception power of the MCS #2,which has the minimum lowest required reception power, to fall withinthe allowable power difference.

As described above, based on the lowest required reception power of eachMCS, the access point 100 sets the target reception power value for eachstation 200 to which corresponding resource is allocated; thus, theminimum necessary transmission power can be set, and the powerconsumption of the station 200 and the interference in another accesspoint 100 can be reduced.

Note that the allowable power difference may be changed depending on theperformance of A/D conversion of the access point 100 as illustrated inFIG. 8A. Changing the allowable power difference depending on theperformance of A/D conversion of the access point 100 makes it possibleto flexibly set the target reception power value with no deteriorationof the performance of reception due to the reception power difference ofthe station 200, and thus the scheduling gain is improved.

In addition, the allowable power difference may be changed depending onthe number of multiplex stations of OFDMA/MU-MIMO as illustrated in FIG.8B. When the number of multiplex stations is small, the reception powerdifference between the stations is likely to be smaller than that whenthe number of multiplex stations is large; thus, changing the allowablepower difference depending on the number of multiplex stations makes itpossible to flexibly set the target reception power value, and hence thescheduling gain is improved.

<Target Reception Power Setting Method 2 (Specific Allocation)>

With reference to the station information indicating the resourceallocated by the specific allocation, which is determined by thescheduling unit 101, the target reception power setting unit 102determines the target reception power value based on the difference ofthe reception power between signals that the concerned station 200received in the past.

FIG. 7B illustrates an example of a method of determining the targetreception power according to the target reception power setting method 2(specific allocation) in the setting method 1. In FIG. 7B, assuming thatthe scheduling unit 101 allocates the resources to the three stations(ID=1, 2, 3), the target reception power setting unit 102 sets theoffsets (offsets 1 to 3) to make the power difference fall within theallowable power difference based on the reception power difference ofthe signal received by the concerned station in the past.

As described above, the access point 100 sets the target reception powervalue based on the reception power of the signal received in the past,and thus the change of the target reception power value of each station200 can be suppressed.

Note that, like the target reception power setting method 1 (specificallocation), the allowable power difference may be changed depending onthe performance of A/D conversion and the number of multiplex stationsof OFDMA/MU-MIMO as illustrated in FIGS. 8A and 8B.

<Target Reception Power Setting Method 3 (Specific Allocation)>

Using the station information indicating the resource allocated by thespecific allocation, which is determined by the scheduling unit 101, thetarget reception power setting unit 102 calculates estimated receptionpower based on the maximum transmission power and the path-loss of theconcerned station and determines the target reception power value basedon a difference of the estimated power between the stations allocated tothe resources.

FIG. 7C illustrates an example of a method of determining the targetreception power according to the target reception power setting method 3(specific allocation) in the setting method 1. In FIG. 7C, assuming thatthe scheduling unit 101 allocates the resources to the three stations(ID=1, 2, 3), the target reception power setting unit 102 sets theoffsets (offsets 1 to 3) to make the estimated reception powerdifference between the stations 200 fall within the allowable powerdifference. Note that FIG. 7C is an example of a case where the maximumtransmission power of the stations 200 are equal. For example, thetarget reception power setting unit 102 uses a value included in anassociation request signal as the maximum transmission power of thestation 200.

As described above, the access point 100 sets the target reception powervalue depending on the maximum transmission power and the path-loss ofeach station 200, and this can prevent setting of the target receptionpower value that requires transmission power greater than the maximumtransmission power that the station 200 can set.

Note that, like the target reception power setting method 1 (specificallocation), the allowable power difference may be changed depending onthe performance of A/D conversion and the number of multiplex stationsof OFDMA/MU-MIMO as illustrated in FIGS. 8A and 8B.

Next, hereinafter, target reception power value setting methods 1 to 4in the random access allocation are described severally with referenceto FIGS. 9A to 9C.

<Target Reception Power Setting Method 1 (Random Access Allocation)>

The target reception power setting unit 102 sets an average value of thetarget reception power values of the stations to which the resources areallocated by the specific allocation as the target reception power valueof the random access-allocation RU.

FIG. 9A illustrates a method of determining the target reception poweraccording to the target reception power setting method 1 (random accessallocation) in the setting method 1. The stations with ID=1, 2 arestations to which the resources are allocated by the specificallocation, while the station with ID=0 is a station to which the randomaccess resource is allocated. In addition, the target reception powervalues of the resources of ID=1, 2 are, for example, assumed to bedetermined by any one of the target reception power setting methods 1 to3 (specific allocation). In this case, the target reception powersetting unit 102 calculates the target reception power of the randomaccess resource (ID=0) based on the average value of the targetreception power values of the resources of ID=1, 2.

As described above, the access point 100 sets the average value of thetarget reception power values of the stations to which the resources areallocated by the specific allocation as the target reception power ofthe random access-allocation RU, and thus the difference of thereception power between the random access-allocation station and thespecific-allocation station can be reduced.

<Target Reception Power Setting Method 2 (Random Access Allocation)>

The target reception power setting unit 102 sets the lowest value of thetarget reception power values of the stations to which the resources areallocated by the specific allocation as the target reception power valueof the random access-allocation RU.

FIG. 9B illustrates a method of determining the target reception poweraccording to the target reception power setting method 2 (random accessallocation) in the setting method 1. The stations 200 with ID=1, 2 arestations to which the resources are allocated by the specificallocation, while the station with ID=0 is a station to which the randomaccess resource is allocated. In addition, the target reception powervalues of the resources of ID=1, 2 are assumed to be determined by anyone of the target reception power setting methods 1 to 3 (specificallocation). The target reception power setting unit 102 calculates thetarget reception power value of the random access resource (ID=0) basedon the lowest value of the target reception power values of theresources of ID=1, 2 (in FIG. 9B, the target reception power value ofthe resource of ID=2).

As described above, the access point 100 sets the lowest value of thetarget reception power values of the stations to which the resources areallocated by the specific allocation as the target reception power valueof the random access-allocation RU, and thus the reception powerdifference between the random access-allocation station and anotherstation can be prevented from increasing even when the reception powerof the random access is increased. This is because the reason of theincrease of the reception power of the random access is that the accesspoint 100 may receive signals of multiple stations 200 at once due tocollision.

<Target Reception Power Setting Method 3 (Random Access Allocation)>

The target reception power setting unit 102 sets average reception powerof signals that all the stations or a part of the stations connected tothe access point 100 received in the past as the target reception powervalue.

In the random access allocation, it is impossible to specify the station200 actually transmitting the response signal. Thus, setting the averagereception power of the signals that all the stations or a part of thestations connected to the access point 100 received in the past as thetarget reception power value allows the transmission power required forsatisfying the target reception power value in the random accessallocation to be likely to fall within a range between the minimumtransmission power and the maximum transmission power of the station200.

<Target Reception Power Setting Method 4 (Random Access Allocation)>

The target reception power setting unit 102 sets the target receptionpower to a fixed value depending on purpose.

FIG. 9C illustrates an example of purposes and the target receptionpower values according to a target reception power setting method 4(random access allocation) in the setting method 1. For example, inorder to preferentially receive a signal of the cell edge station, thetarget reception power setting unit 102 sets the target reception powervalue low (e.g., −75 dBm) to allow even the cell edge station to satisfythe predetermined target reception power. Meanwhile, in order topreferentially receive a signal of the station near the access point,the target reception power setting unit 102 sets a required targetreception power value high (e.g., −65 dBm).

As described above, the access point 100 sets the target reception powervalue of the random access-allocation station depending on purpose, andthus the reception from either the cell edge station or the station nearthe access point can be preferentially performed.

The method of setting the target reception power value in the settingmethod 1 is described above.

As described above, in the setting method 1, the access point 100notifies the station 200 of the target reception power value using thestation-specific field of the random access control signal. In addition,the station 200 performs the transmission power control of the responsesignal based on the estimated path-loss and the target reception powervalue provided as notification. This can reduce the reception powerdifference in the access points 100 between the stations 200 to whichthe resources are allocated by the random access control signal, and thecarrier interference and the problem of the dynamic range of A/Dconversion can be solved. In addition, the access point 100 sets thetarget reception power value for every station 200 using the specificfield of the station 200, and thus the transmission power can be set inaccordance with the channel state of each station 200.

<Setting Method 2>

In the setting method 2, the access point 100 (RA control signalgenerating unit 104) arranges the target reception power value in thecommon field of the random access control signal. FIG. 10 illustrates anexample of the random access control signal according to the settingmethod 2. The Trigger type in FIG. 10 indicates a type of the triggerframe and, for example, the Trigger type is set to indicate that thetrigger frame is the random access control signal.

After receiving the random access control signal, the station 200obtains the target reception power value arranged in the station-commonfield. Then, based on the path-loss calculated by the path-lossestimating unit 207 and the above-described obtained target receptionpower value, the station 200, for example, calculates the transmissionpower of the response signal using Equation (3) and performs thetransmission power control on the response signal.

Note that, since the target reception power values of the stations 200are made equal in this example of setting, the reception qualities ofthe stations 200 are almost the same. The access point 100 can uniquelydetermine the MCSs of the stations 200 based on the common targetreception power value. Thus, a configuration for transmitting theinformation such as the MCS using the common field instead of using thestation-specific field may be applied. Transmitting the MCS using thecommon field can reduce the overhead of the random access controlsignal.

Target Reception Power Value Setting Method

Next, a method of setting the target reception power value in the accesspoint 100 when the setting method 2 is applied is described.

Hereinafter, target reception power value setting methods 1′ to 3′ forthe specific allocation are described severally with reference to FIGS.11A to 11C.

<Target Reception Power Setting Method 1′ (Specific Allocation)>

With reference to the station information indicating the resourceallocated by the specific allocation and the MCS of each station, whichare determined by the scheduling unit 101, the target reception powersetting unit 102 determines the target reception power value based onthe lowest required reception power of the highest MCS.

FIG. 11A illustrates an example of a method of determining the targetreception power according to the target reception power setting method1′ (specific allocation) in the setting method 2. In FIG. 11A, theresources (RU=1, 2, 3) are respectively allocated to the three stations(ID=1, 2, 3). The MCSs of the respective stations 200 are #2, #3, and#5.

The target reception power setting unit 102 adds an offset to the lowestrequired reception power of the highest MCS among the MCSs #2, #3, and#5 of the stations 200, or the MCS #5 of the station ID=3, and sets thatvalue as the target reception power value common for the stations 200.

As described above, the access point 100 sets the target reception powervalue common for all the stations 200 based on the highest MCS among theMCSs set in the stations 200, and thus the access point 100 can be morelikely to receive the response signals of all the stations with noerrors.

<Target Reception Power Setting Method 2′ (Specific Allocation)>

With reference to the station information indicating the resourceallocated by the specific allocation, which is determined by thescheduling unit 101, the target reception power setting unit 102determines the target reception power value based on an average value ofthe reception power of the signals that the station 200 received in thepast.

FIG. 11B illustrates an example of a method of determining the targetreception power according to the target reception power setting method2′ (specific allocation) in the setting method 2. In FIG. 11B, assumingthat the scheduling unit 101 allocates the resources to the threestations 200 (ID=1, 2, 3), the target reception power setting unit 102sets the average value of the reception power of the signals received bythe station 200 in the past as the target reception power value commonfor the stations 200.

As described above, the access point 100 sets the average value of thereception power of the signals received by the station 200 in the pastas the target reception power value, and thus the transmission powerrequired for satisfying the target reception power value is likely tofall within the range between the minimum transmission power and themaximum transmission power of each station 200.

<Target Reception Power Setting Method 3′ (Specific Allocation)>

Using the station information indicating the resource allocated by thespecific allocation, which is determined by the scheduling unit 101, thetarget reception power setting unit 102 calculates estimated receptionpower based on the maximum transmission power and the path-loss of theconcerned station 200 and determines the estimated reception power ofthe station 200 having the lowest estimated reception power as thetarget reception power value common for the stations 200.

FIG. 11C illustrates an example of a method of determining the targetreception power according to the target reception power setting method3′ (specific allocation) in the setting method 2. In FIG. 11C, assumingthat the scheduling unit 101 allocates the resources to the threestations 200 (ID=1, 2, 3), the target reception power setting unit 102sets the estimated reception power of the station 200 having the lowestestimated reception power among the stations 200, or the station ID=3,as the target reception power value common for the stations 200.

As described above, the access point 100 estimates the target receptionpower based on the maximum transmission power and the path-loss of eachstation 200 and sets the target reception power of the station 200having the lowest target reception power as the target reception powervalue common for the stations 200; thus, the target reception power canbe set low, and the consumed power of the station 200 and theinterference in another access point 100 can be reduced. In addition,this can prevent the station 200 from setting the target reception powervalue that requires transmission power greater than the settable maximumtransmission power.

Next, hereinafter, a method of setting the target reception power valuein the random access allocation is described.

<Target Reception Power Setting Method (Random Access Allocation)>

The target reception power setting unit 102 may use a setting methodsimilar to the target reception power setting methods 1′ to 3′ in theabove-described setting method 2 to set the target reception power valuethat is set to be common for the stations 200 to which the resources areallocated by the specific allocation as the target reception power valueof the random access-allocation RU. Note that the target reception powersetting unit 102 may use a setting method similar to the targetreception power setting method 3 (random access allocation) and thetarget reception power setting method 4 (random access allocation) inthe setting method 1 to set the target reception power value.

The method of setting the target reception power value in the settingmethod 2 is described above.

As described above, in the setting method 2, the access point 100arranges the target reception power value in the common field of therandom access control signal as illustrated in FIG. 10 , and thus thetime length of the station-specific field can be shortened, and theoverhead of the random access control signal can be reduced. The accesspoint 100 cannot specify which station 200 among the randomaccess-allocation stations 200 transmits the response signal and cannotindividually set an appropriate value of the target reception powervalue to the stations 200. Thus, in a case where the proportion of therandom access-allocation stations 200 is high, the performancedeterioration is little even when the target reception power value isarranged in the common field.

<Setting Method 3>

In the setting method 3, like the setting method 2, the access point 100(RA control signal generating unit 104) arranges the target receptionpower value in the common field of the random access control signal.Note that the target reception power value is set to different valuesfor each type of the response signal (information) transmitted by therandom access.

The type of the response signal may be, for example, data, controlinformation, and management information. FIG. 12 illustrates an exampleof the target reception power value of each type of the response signalaccording to the setting method 3. A high target reception power valueis set when the degree of importance of the response signal is high,while a low target reception power value is set when the degree ofimportance of the response signal is low. The example in FIG. 12illustrates a case where the priority is high in order of the controlinformation, the data, and the management information.

Note that the high target reception power value means that, for example,an offset of ZdB is added to the target reception power value calculatedwith the setting method 2. Likewise, the low target reception powervalue means that, for example, an offset of YdB is added to the targetreception power value calculated with the setting method 2 (however,Y<Z).

In addition, for example, the response signal of high importance is asignal in which its value is updated frequently, while the responsesignal of low importance is a signal in which its value is not updatedfrequently.

Moreover, the type of the response signal may not be classified into thedata, the control information, and the management information, and, forexample, the management information may be further classified indetails, and the target reception power value for every Probe Responseand Association Response may be provided as notification.

After receiving the random access control signal, the station 200obtains multiple target reception power values arranged in thestation-common field and switches the target reception power value foruse depending on the type of the signal transmitted as the responsesignal. Then, based on the path-loss calculated by the path-lossestimating unit 207 and the above-described selected target receptionpower value, the station 200, for example, calculates the transmissionpower of the response signal using Equation (3) and performs thetransmission power control on the response signal.

As described above, in the setting method 3, the access point 100arranges the target reception power value in the common field of therandom access control signal as illustrated in FIG. 10 and also sets thetarget reception power value to a different value for each type of theresponse signal. In this way, even when the response signals collide inthe random access, the response signal to which the high targetreception power value is set is likely to be received with no errors inthe access point 100, and thus the probability of successful receptionof the signal of high importance can be increased.

<Setting Method 4>

In the setting method 4, like the setting method 2, the access point 100arranges the target reception power value in the common field of therandom access control signal. Note that the target reception power valueis provided as notification in each of the specific allocation and therandom access allocation.

FIG. 13 illustrates an example of the target reception power value foreach allocation method according to the setting method 4. When theallocation method is the specific allocation, no collision of theresponse signals occurs, or the maximum transmission power and theminimum transmission power of the station 200 to which the access point100 allocates the resource can be estimated in advance. Thus, thedifference between the reception power of the response signal that theaccess point 100 actually receives and the target reception power valueis thought to be small. Hence, when the allocation method is thespecific allocation, the access point 100 sets the target receptionpower value relatively high.

On the other hand, the collision of the response signals may occur whenthe allocation method is the random access allocation, and theoccurrence of the collision makes the difference between the receptionpower of the response signal and the target reception power value large.That is, it can be thought that the reception power of the responsesignal is likely to become greater than the target reception powervalue. Hence, when the allocation method is the random accessallocation, the access point 100 sets the target reception power valuerelatively low.

After receiving the random access control signal, the station 200obtains the multiple target reception power values arranged in thestation-common field. Based on the station identification ID in thestation-specific field, the station 200 determines whether the resourceused for transmitting the response signal is the resource allocated bythe random access allocation. That is, the station 200 determines thatthe allocation method is the specific allocation when the stationidentification ID is the ID of own device, and determines that theallocation method is the random access allocation when the stationidentification ID is the random access ID. Depending on whether theallocation method is the specific allocation or the random accessallocation, the station 200 switches the target reception power valueused for transmitting the response signal. Then, based on the path-losscalculated by the path-loss estimating unit 207 and the above-describedselected target reception power value, the station 200, for example,calculates the transmission power of the response signal using Equation(3) and performs the transmission power control on the response signal.

As described above, in the setting method 4, the access point 100arranges the target reception power value in the common field of therandom access control signal as illustrated in FIG. 10 and also sets thetarget reception power value to a different value for each of theallocation methods (specific allocation, random access allocation). Inthis way, for example, since the reception power in the random accessallocation is increased when the collision occurs, the access point 100in the random access allocation sets the target reception power valueconsidering the increase of the reception power due to the collision,and thus the performance deterioration of the A/D conversion andincrease of the interference in another station when the collisionoccurs can be prevented.

<Setting Method 5>

In the setting method 5, the access point 100 arranges the targetreception power value in the common field of the random access controlsignal. Further, the access point 100 arranges in the station-specificfield an offset value from the target reception power value set to thecommon field (a target reception power offset).

FIG. 14 illustrates an example of the random access control signalaccording to the setting method 5. The Trigger type in FIG. 14 indicatesa type of the trigger frame and, for example, the Trigger type is set toindicate that the trigger frame is the random access control signal.

After receiving the random access control signal, the station 200obtains the target reception power value arranged in the station-commonfield. Further, the station 200 obtains the target reception poweroffset arranged in the station-specific field to which the STA_ID of thestation 200 (own device) or the random access ID is set as the stationidentification ID and then adds the target reception power offset to thetarget reception power value obtained from the common field. Then, basedon the path-loss calculated by the path-loss estimating unit 207 and theabove-described obtained target reception power value, the station 200,for example, calculates the transmission power of the response signalusing Equation (3) and performs the transmission power control on theresponse signal.

Target Reception Power Value Setting Method

Next, a method of setting the target reception power value in the accesspoint 100 when the setting method 5 is applied is described.

FIG. 15 is an example of a pattern of the target reception power offsetaccording to the setting method 5. FIG. 15 illustrates the offset valueswhen the target reception power offset is indicated by 2 bits. Note thatthe target reception power offset value may be any bit number as long asthat the value is smaller than the bit number of the target receptionpower value.

The target reception power value when the setting method 5 is applied iscalculated in the procedure similar to the setting method 1. Note that,in the setting method 1, the target reception power value individuallyset to the station 200 is set to the station-specific field of therandom access control signal, but in the setting method 5, the accesspoint 100, for example, calculates an average value of the targetreception power values obtained for each station 200 and sets theaverage value to the common field of the random access control signal.Further, the access point 100 measures a difference between the targetreception power value of each station 200 and the average value,quantizes the difference of the averaged target reception power valueusing the table in FIG. 15 , generates the target reception poweroffset, and sets that to the station-specific field.

As described above, in the setting method 5, the access point 100arranges the target reception power value in the common field of therandom access control signal as illustrated in FIG. 14 and also arrangesin the station-specific field the offset value from the target receptionpower value set to the common field. In this way, since the bit numberof the target reception power offset is smaller than the bit number ofthe target reception power value, the total time length of the commonfield and the station-specific field can be shortened when there aremany stations of the allocation, and thus the overhead of the randomaccess control signal can be reduced.

<Setting Method 6>

In the setting method 6, the access point 100 sets differenttransmission power control information to the station-specific field ofthe random access control signal for the specific-allocation station andthe random access-allocation station. For instance, the access point 100arranges a transmission power value for transmitting the upstream signalin the station-specific field for the specific-allocation station, andarranges the target reception power value in the station-specific fieldfor the random access-allocation station.

FIG. 16 illustrates an example of the random access control signalaccording to the setting method 6. The Trigger type in FIG. 16 indicatesa type of the trigger frame and, for example, the Trigger type is set toindicate that the trigger frame is the random access control signal.

The access point 100 arranges the transmission power value in a field ofthe station-specific field to which the control signal for the specificallocation, or the unique ID (STA_ID) for discriminating the station200, is set. On the other hand, the access point 100 arranges the targetreception power value in a field of the station-specific field to whichthe control signal for the random access allocation, or the randomaccess ID (RA_ID), is set.

After receiving the random access control signal, when there is thestation-specific field to which the STA_ID of the station 200 is set asthe station identification ID, the station 200 obtains the transmissionpower value arranged in the concerned station-specific field andperforms the transmission power control on the response signal based onthe obtained transmission power. On the other hand, when there is thestation-specific field to which the random access ID is set as thestation identification ID, the station 200 obtains the target receptionpower value arranged in the concerned station-specific field, and, basedon the path-loss calculated by the path-loss estimating unit 207 and theabove-described obtained target reception power value, the station 200,for example, calculates the transmission power of the response signalusing Equation (3) and performs the transmission power control on theresponse signal.

Target Reception Power Value Setting Method

Next, a method of setting the target reception power value in the accesspoint 100 when the setting method 6 is applied is described. Like thesetting method 1, the access point 100 obtains the target receptionpower value of each station 200.

Since the transmission power needs to be set to the specific-allocationstation in the setting method 6, the access point 100, for example,calculates the transmission power of the station 200 using Equation (3).Then, for the specific-allocation station, the access point 100 sets thecalculated transmission power value to the station-specific field of therandom access control signal. Note that the format (bit number) of thetarget reception power value and the transmission power value may be thesame.

As described above, when the station 200 is not notified of thetransmission antenna gain and the transmission antenna gain has a largeeffect, calculating the transmission power by the access point 100 forthe specific-allocation station allows the transmission power control tobe performed more accurately. In addition, since the path-losscalculation processing and the transmission power calculation processingin the station 200 side can be omitted by notifying thespecific-allocation station of the transmission power, the powerconsumption of the station 200 can be reduced. Moreover, when theformats (bit numbers) of the transmission power value and the targetreception power value are the same, the position to which the stationidentification ID is set is the same as before; thus, there is noincrease of complexity of the processing for determining the position ofthe station identification ID.

<Setting Method 7>

In the setting method 7, the access point 100 arranges the targetreception power value for the random access-allocation station in thecommon field of the random access control signal and arranges the targetreception power value for the specific-allocation station in thestation-specific field of the random access control signal.

FIG. 17 illustrates an example of the random access control signalaccording to the setting method 7. The Trigger type in FIG. 17 indicatesa type of the trigger frame and, for example, the Trigger type is set toindicate that the trigger frame is the random access control signal. Theaccess point 100 arranges the target reception power value in thestation-specific field to which the unique ID (STA_ID) fordiscriminating the station 200 is set and arranges no target receptionpower value in the station-specific field to which the random access ID(RA_ID) is set. In addition, the access point 100 arranges the targetreception power value for the random access-allocation station in thecommon field.

After receiving the random access control signal, when there is thestation-specific field to which the STA_ID of the station 200 is set asthe station identification ID, the station 200 obtains the targetreception power value arranged in the concerned station-specific fieldand performs the transmission power control of the response signal basedon the obtained target reception power value. On the other hand, when noSTA_ID of the station 200 is set as the station identification ID, thestation 200 obtains the target reception power value arranged in thecommon field, and, based on the path-loss calculated by the path-lossestimating unit 207 and the above-described obtained target receptionpower value, the station 200, for example, calculates the transmissionpower of the response signal using Equation (3) and performs thetransmission power control on the response signal.

As described above, in the setting method 7, the access point 100arranges the target reception power value in the common field of therandom access control signal for the random access-allocation station asillustrated in FIG. 17 and arranges the target reception power value inthe station-specific field of the random access control signal for thespecific-allocation station. This allows the total time length of thecommon field and the station-specific field to be shortened when thereare many random access-allocation stations, and thus the overhead of therandom access control signal can be reduced. In addition, the accesspoint 100 cannot specify which station 200 among the randomaccess-allocation stations transmits the response signal and cannotindividually set an appropriate value of the target reception powervalue to the stations 200. Hence, in a case where the proportion of therandom access-allocation station 200 is high, the performancedeterioration is little even when the target reception power value isarranged in the common field.

The transmission power control information and field setting methods 1to 7 in this embodiment are described above.

Path-loss Feedback Timing

Next, timing when the station 200 provides the path-loss as feedback tothe access point 100 in a case where the access point 100 uses thepath-loss to calculate the target reception power value in thisembodiment is described.

Hereinafter, timing 1 to 4 when the station 200 provides the path-lossas feedback is severally described.

<Timing 1>

In the timing 1, the station 200 transmits a path-loss notificationsignal to the access point 100 as a response to a request signal(path-loss request signal) from the access point 100. FIG. 18illustrates an example of a sequence of processing of the path-lossfeedback according to the timing 1.

In FIG. 18 , the access point 100 generates a beacon signal (ST201). Thebeacon signal includes the transmission power of the access point 100.

The access point 100 wirelessly notifies the station 200 of thegenerated beacon signal (ST202).

Next, the access point 100 regularly generates the path-loss requestsignal (ST203). The path-loss request signal is generated as an actionframe, for example. The action frame is a frame for setting MeasurementRequest, TPC request, and the like (e.g., see IEEE STD 802.11H-2003).

The access point 100 wirelessly notifies the station 200 of thegenerated path-loss request signal (ST204).

When receiving the path-loss request signal, the station 200 estimatesthe path-loss based on the transmission power, the antenna gain, and thelike that are provided as notification by the beacon signal, and thelike (ST205). The path-loss estimation is represented by Equation (1) orEquation (2), for example.

Next, the station 200 generates a path-loss notification signal (ST206).The path-loss notification signal is generated as the action frame, forexample.

The station 200 wirelessly notifies the access point 100 of thegenerated path-loss notification signal (ST207).

As described above, in the timing 1, the station 200 transmits thepath-loss to the access point 100 as a response to the path-loss requestsignal. This allows the station 200 to notify the access point 100 ofthe path-loss in timing when the access point 100 needs the path-loss.

<Timing 2>

In the timing 2, the station 200 regularly estimates the path-loss, andwhen the amount of path-loss change from the last timing when thepath-loss is provided as notification reaches a certain criterion, orwhen a certain time passed from the last timing when the path-loss isprovided as notification, the station 200 transmits the path-lossnotification signal to the access point 100. FIG. 19 illustrates anexample of a sequence of processing of the path-loss feedback accordingto the timing 2.

In FIG. 19 , the access point 100 generates a beacon signal (ST211). Thebeacon signal includes the transmission power of the access point 100.

The access point 100 wirelessly notifies the station 200 of thegenerated beacon signal (ST212).

The station 200 regularly estimates the path-loss based on thetransmission power, the antenna gain, and the like that are provided asnotification by the beacon signal (ST213). The path-loss estimation isrepresented by Equation (1) or Equation (2), for example. The signalused in the path-loss estimation may be a signal that is receivedimmediately before the path-loss estimation.

As for the estimated path-loss, the station 200 determines whether theamount of path-loss change from the last timing when the path-loss isprovided as notification reaches the certain criterion, or whether acertain time passed from the last timing when the path-loss is providedas notification.

When the determination condition is satisfied, the station 200 generatesthe path-loss notification signal (ST215). The path-loss notificationsignal is generated as the action frame, for example.

The station 200 wirelessly notifies the access point 100 of thegenerated path-loss notification signal (ST216).

As described above, in the timing 2, the station 200 notifies the accesspoint 100 of the path-loss only at the timing when the path-loss ischanged. This can reduce the overhead of the control information.

<Timing 3>

In the timing 3, the station 200 determines the access point 100 to beconnected and includes the path-loss estimated by the station 200 intothe association request signal when transmitting the association requestsignal. FIG. 20 illustrates an example of a sequence of processing ofthe path-loss feedback according to the timing 3.

In FIG. 20 , the access point 100 generates a beacon signal (ST221). Thebeacon signal includes the transmission power of the access point 100.

The access point 100 wirelessly notifies the station 200 of thegenerated beacon signal (ST222).

The station 200 selects the access point 100 as a connection destinationbased on the reception quality and the like (ST223).

The station 200 estimates the path-loss based on the transmission power,the antenna gain, and the like that are provided as notification by thebeacon signal (ST224). The path-loss estimation is represented byEquation (1) or Equation (2), for example.

The station 200 generates the association request signal (ST225). Theassociation request signal is a signal for notifying the access point100 as the connection destination of the information on the station 200(e.g., see IEEE STD 802.11-2012). The station 200 includes the estimatedpath-loss into this association request signal.

The station 200 wirelessly notifies the access point 100 of thegenerated association request signal (ST226).

As described above, in the timing 3, the path-loss is included in theassociation request signal, and thus the overhead of the controlinformation can be more reduced than a case where the path-loss istransmitted independently.

<Timing 4>

In the timing 4, the station 200 includes the path-loss estimated by thestation 200 into the buffer status report when transmitting the bufferstatus report as a response to the random access control signal. FIG. 21illustrates an example of a sequence of processing of the path-lossfeedback according to the timing 4.

In FIG. 21 , the access point 100 generates a beacon signal (ST231). Thebeacon signal includes the transmission power of the access point 100.

The access point 100 wirelessly notifies the station 200 of thegenerated beacon signal (ST232).

In order to check the buffer status of the station 200, the access point100 generates the random access control signal for requesting the bufferstatus report (ST233).

The access point 100 wirelessly notifies the station 200 of thegenerated random access control signal (ST234).

The station 200 estimates the path-loss based on the transmission power,the antenna gain, and the like that are provided as notification by thebeacon signal (ST235). The path-loss estimation is represented byEquation (1) or Equation (2), for example.

The station 200 generates the buffer status report for providing thebuffer status of own device as notification (ST236). The station 200also includes the estimated path-loss into this buffer status report.

The access point 100 wirelessly notifies the station 200 of thegenerated buffer status report (ST237).

As described above, in the timing 4, the station 200 simultaneouslytransmits the buffer status report and the path-loss, and thus theoverhead of the control information can be more reduced than a casewhere the path-loss is transmitted independently. In addition, thebuffer status report and the path-loss are used for scheduling of therandom access and the transmission power control, and since the timingof use is the same, the efficiency is improved by this simultaneousfeedback.

The path-loss feedback timings 1 to 4 are described above.

As described above, in this embodiment, the access point 100 notifiesthe station 200 of the target reception power value using the randomaccess control signal, and the station 200 calculates the transmissionpower based on the estimated path-loss and the target reception powervalue provided as notification and performs the transmission powercontrol. In this way, the access point 100 can reduce the receptionpower difference between the stations 200 when the multiple stations 200receive the multiplexed signals via UL MU-MIMO or OFDMA. Thus, it ispossible to reduce the MU interference and make the reception signalfall within the dynamic range of A/D conversion. As described above,according to this embodiment, the transmission power control iseffectively performed in the UL response signal for the MU transmissionby the random access, and the reception power difference between thestations 200 is reduced; thus, the carrier interference and the problemof the dynamic range of A/D conversion can be solved.

In addition, in this embodiment, the target reception power value isprovided as notification using the random access control signal, andthus the target reception power value can be dynamically changed atevery scheduling depending on the reception qualities of the randomaccess-allocation station or the specific-allocation station; hence, theoptimum adaptation modulation can be immediately applied to each station200. This can improve the system throughput in this embodiment.

Embodiment 2

As described above, the access point notifies the station of the targetreception power value using the random access control signal andperforms the transmission power control at the station side, and thusthe reception power difference between the stations in the access pointcan be reduced when the access point receives a signal in which signalsfrom the multiple stations are multiplexed via UL MU-MIMO or OFDMA.

However, an 11ax-compliant station has low performance of thetransmission power control. For example, among the 11ax-compliantstations, there may be a station that can change the transmission powerfor only few stages and a station that has no function of thetransmission power control in some cases. Thus, in each station,regardless of the calculation of the transmission power based on thetarget reception power value and the like provided as notification, theresponse signal may not be transmitted with the transmission powersatisfying the target reception power value on the access point side,due to the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation.

Thus, in this embodiment, a method of controlling transmission of thestation when it is difficult to satisfy the target reception power valuedue to the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation. This can reduce the reception power difference between thestations in the access point.

FIG. 22 is a block diagram that illustrates a configuration of a station300 according to this embodiment. FIG. 22 differs from FIG. 5 in thatthe information outputted by the transmission power calculating unit 205and the information outputted by the RA control signal decoding unit 204are inputted to a transmission control unit 301, and the output of thetransmission control unit 301 is inputted to the radiotransmitting-receiving unit 202. In addition, the configuration of theaccess point 100 is the same as that in Embodiment 1 (FIG. 4 ).

This embodiment differs from Embodiment 1 in that the transmissioncontrol unit 301 controls the radio transmitting-receiving unit 202depending on a value of the calculated transmission power and stops thetransmission of the signal (details are described later).

Based on the target reception power value inputted from the RA controlsignal decoding unit 204 and the path-loss value inputted from thepath-loss estimating unit 207, the transmission power calculating unit205, for example, calculates the transmission power using Equation (3).

Based on the transmission power value inputted from the transmissionpower calculating unit 205, the information inputted from the RA controlsignal decoding unit 204 (target reception power value and the like),and the maximum transmission power, the minimum transmission power, andthe transmission power variable range of the station 300, in terms ofwhether it is possible to set the transmission power satisfying thecondition that the transmission power falls within the allowable powerdifference of the target reception power value, the transmission controlunit 301 determines whether to stop the transmission of the concernedsignal and outputs information indicating whether to stop thetransmission, to the radio transmitting-receiving unit 202. Note that amethod of determining whether to stop the transmission is describedlater.

When there is an instruction to stop the transmission from thetransmission control unit 301, the radio transmitting-receiving unit 202does not transmit the concerned signal. On the other hand, when there isno instruction to stop the transmission from the transmission controlunit 301, the radio transmitting-receiving unit 202 performspredetermined radio transmitting processing such as D/A conversion on asignal inputted from the transmission signal generating unit 210 and upconversion on the carrier frequency, and transmits the radiotransmission processed signal via the antenna 201.

Hereinafter, determining methods 1 to 6 of determining whether to stopthe transmission are described severally.

<Determining Method 1>

In the determining method 1, the transmission control unit 301 issues noinstruction to stop the transmission with any transmission power.

As described above, in the determining method 1, since the transmissioncontrol unit 301 issues no instruction to stop the transmission,depending on the limits of the transmission power, the power differenceof the reception signals in the access point 100 may be equal to orgreater than a predetermined value when there are many stations 300 towhich no transmission power falling within the allowable powerdifference of the target reception power value can be set. However, whenthe number of the stations is small, the reception power difference islikely to fall within the predetermined range; thus, if the transmissioncontrol unit 301 issues no instruction to stop the transmission, theresource can be effectively used. In addition, when the performance ofA/D conversion of the access point 100 is high, there is no problem ofthe dynamic range of A/D conversion due to the transmission powerdifference.

<Determining Method 2>

In the determining method 2, when no transmission power falling withinthe allowable power difference of the target reception power value canbe set as the transmission power calculated by the transmission powercalculating unit 205 due to the limits of the maximum transmissionpower, the minimum transmission power, and the transmission powervariable range of the station 300, the transmission control unit 301issues the instruction to stop the transmission.

As described above, when no transmission power falling within theallowable power difference of the target reception power value of thestation 300 can be set, the transmission control unit 301 always stopsthe transmission. This can prevent the reception power differencebetween the stations 300 from increasing due to the unsatisfied targetreception power value. In addition, stopping the transmission of thesignal that may fail with the reception due to the unsatisfied targetreception power value can decrease the probability of collision in therandom access allocation.

<Determining Method 3>

In the determining method 3, in the specific allocation, thetransmission control unit 301 issues no instruction to stop thetransmission with any transmission power. On the other hand, in therandom access allocation, when no transmission power falling within theallowable power difference of the target reception power value can beset due to the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation 300, the transmission control unit 301 issues the instruction tostop the transmission.

As described above, the station 300 issues the instruction to stop thetransmission depending on the transmission power only to the station 300for which the target reception power value is possibly set in the accesspoint 100 in the random access allocation where it cannot be determinedwhich station 300 actually transmits the response signal in the accesspoint 100, that is, in a situation where the transmission power controlperformance such as the maximum transmission power and the minimumtransmission power of the station 300 is unknown. This can prevent thereception power difference between the stations 300 from increasing dueto the unsatisfied target reception power value. On the other hand, inthe specific allocation, the target reception power value can be set inthe access point 100 while taking into consideration the transmissionpower control performance such as the maximum transmission power and theminimum transmission power of the station 300 to which the resource isallocated. Thus, since the target reception power value is rarelychanged a lot because of the limit of the transmission power, alwaystransmitting the response signal in the specific-allocation stationregardless of the transmission power can increase the efficiency of useof the resource.

<Determining Method 4>

In the determining method 4, the access point 100 signals the station300 of whether to stop the transmission when no transmission powerfalling within the allowable power difference of the target receptionpower value can be set due to the limits of the maximum transmissionpower, the minimum transmission power, and the transmission powervariable range of the station 300. Based on the signaling (0: do nottransmit, 1: transmit), the station 300 indicates whether to stop thetransmission.

As described above, the station 300 shifts whether to stop thetransmission by the signaling from the access point 100 when notransmission power falling within the allowable power difference of thetarget reception power value can be set, and thus the transmissioncontrol can be changed depending on the performance of A/D conversion ofthe access point 100.

<Determining Method 5>

In the determining method 5, in the specific allocation, thetransmission control unit 301 issues no instruction to stop thetransmission with any transmission power, and in the random accessallocation, depending on BSS LOAD provided as notification by thebeacon, the transmission control unit 301 issues the instruction to stopthe transmission when no transmission power falling within the allowablepower difference of the target reception power value can be set due tothe limits of the maximum transmission power, the minimum transmissionpower, and the transmission power variable range of the station 300.That is, the transmission control unit 301 issues no instruction to stopthe transmission when BSS LOAD is low and issues the instruction to stopthe transmission when BSS LOAD is high. BSS LOAD is information that theaccess point 100 notifies the station 300 by the beacon of thecongestion degree based on the number of stations connected to the BSSand the traffic state (e.g., see IEEE STD 802.11-2012).

As described above, the station 300 shifts whether to stop thetransmission in the random access allocation depending on BSS LOAD and,when the possibility of collision in the random access is high (that is,when BSS LOAD is high), stops the transmission of the signal that mayfail with the reception due to the unsatisfied target reception powervalue; thus, the collision probability in the random access can bedecreased.

<Determining Method 6>

In the determining method 6, in the specific allocation, thetransmission control unit 301 issues no instruction to stop thetransmission with any transmission power, and in the random accessallocation, the transmission control unit 301 shifts whether to stop thetransmission depending on the type of the response signal.

The type of the response signal may be, for example, the data, thecontrol information, and the management information. FIG. 23 illustratesan example that the transmission is stopped or not depending on the typeof the response signal according to the determining method 6. When thetype of the response signal is of high importance, the transmissioncontrol unit 301 issues no instruction to stop the transmission with anytransmission power. On the other hand, when the type of the responsesignal is of low importance and when no transmission power fallingwithin the allowable power difference of the target reception powervalue can be set due to the limits of the maximum transmission power,the minimum transmission power, and the transmission power variablerange of the station 300, the transmission control unit 301 issues theinstruction to stop the transmission.

As described above, the station 300 shifts whether to stop thetransmission in the random access allocation depending on the type ofthe response signal, and thus it is possible to prevent a situationwhere the signal of high importance cannot be transmitted in the randomaccess. Note that the operation in response to the instruction to stopthe transmission is not limited to completely stopping the transmission.For example, an operation may be allowed to decrease the priority byreducing the transmission probability of the random access.

The methods 1 to 6 of determining whether to stop the transmission inthe transmission control unit 301 are described above.

Note that the access point 100 may notify the station 300 of theshifting of the above-described determining methods using the managementframe such as the beacon, Probe Response, and Association Response, andmay include the shifting into the random access control signal to bebroadcast to the station 300. Controlling by the management frame makesit possible to set an appropriate value for each BSS. In addition, eventhough performing the control at every transmission of the random accesscontrol signal increases the overhead, in an environment where the stateof the station 300 greatly changes, appropriate control following thatchanges can be achieved.

As described above, in this embodiment, the transmission control unit301 stops the transmission processing of the station 300 depending onthe situation when the station 300 cannot transmit the UL responsesignal with the transmission power satisfying the target reception powerprovided as notification from the access point 100 due to thetransmission power control capability (performance) the limits of themaximum transmission power, the minimum transmission power, and thetransmission power variable range of the station 300. This can reducethe reception power difference between the stations 300 in the accesspoint 100 regardless of the limits of the performance of the station300, or the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation 300. Hence, according to this embodiment, it is possible toreduce the MU interference and make the reception signal fall within thedynamic range of A/D conversion, and thus the system throughput can beimproved.

Embodiment 3

As described above, the station stops the transmission of the responsesignal that cannot satisfy the target reception power depending on thesituation, and thus the reception power difference between the stationsin the access point can be reduced regardless of the performance of thestation. However, depending on the setting of the target reception powervalue, stopping the transmission may increase the number of the stationsthat have significantly decreased opportunities for transmitting theresponse signal.

Thus, in this embodiment, a method of preventing the significantdecrease of the opportunities for transmitting the response signal of aspecific station, such as a station with a low capability in controllingthe transmission power, by changing the target reception power value andthe like at every transmission when the random access control signalsare successively transmitted.

FIG. 24 is a block diagram that illustrates a configuration of an accesspoint 400 according to this embodiment. FIG. 24 differs from FIG. 4 inthat the resource allocation information determined by the schedulingunit 101 and the target reception power value calculated by the targetreception power setting unit 102 are inputted to a transmission controlunit 401, and the transmission control unit 401 outputs information forinstructing control to the scheduling unit 101 and the target receptionpower setting unit 102. Note that the configuration of the station 300is the same as that in Embodiment 2 (FIG. 22 ).

This embodiment differs from Embodiment 1 in that, when the randomaccess control signals are successively transmitted, the transmissioncontrol unit 401 controls operations of the scheduling unit 101 and thetarget reception power setting unit 102 at every one of successivetransmissions (details are described later).

The resource allocation information determined by the scheduling unit101 and the target reception power value calculated by the targetreception power setting unit 102 are inputted to the transmissioncontrol unit 401. The transmission control unit 401 stores the inputtedresource allocation information (including the MCS) and the targetreception power value at every transmission of the random access controlsignal.

When the successive random access control signals are transmitted, thetransmission control unit 401 controls the target reception power valueincluded in the random access control signal. Specifically, when therandom access control signals are successively transmitted, based on thetarget reception power value provided as notification to the station 300using the random access control signal in the past and the resourceallocation information, the transmission control unit 401 controls thescheduling unit 101 and the target reception power setting unit 102 toset different target reception power value and the resource allocationinformation at every successive transmission. Note that the controllingmethod in the transmission control unit 401 is described later.

Based on the contents indicated by the transmission control unit 401,the scheduling unit 101 determines the resource allocation and outputsthe resource allocation information to the transmission power controlinformation setting unit 103 and the RA control signal generating unit104. The target reception power setting unit 102 sets the targetreception power value based on the contents indicated by thetransmission control unit 401 and outputs the target reception powervalue to the transmission power control information setting unit 103.

FIG. 25 illustrates an example of the UL MU transmission procedure forsuccessively transmitting the random access control signals (TF-Rs)according to Embodiment 3.

In FIG. 25 , in the UL MU transmission procedure within a TXOP sectionin the access point 400 (AP) that acquires a transmission right by theCSMA/CA, TF-R#1 is a first random access control signal to betransmitted, and TF-R#2 is a second random access control signal to betransmitted. In addition, in FIG. 25 , ULMU is the UL response signal,and ACK (or multi-STA block ACK (M-BA)) is information indicating thesuccess in receiving the UL response signal. In addition, in FIGS. 25 ,P1 and P2 are the target reception power values in every transmission.

Note that the successive transmission means that the random accesscontrol signals are successively transmitted in the TXOP. Afteracquiring the transmission right by the CSMA/CA, the access point 400counts the number of the transmission. The access point 400 sets thetarget reception power value applied to the first random access controlsignal to be transmitted (TF-R#1) using any one of the target receptionpower setting methods (random access allocation) of Embodiment 1.

Hereinafter, controlling methods 1 to 3 of the transmission control unit401 are described severally.

<Controlling Method 1>

In the controlling method 1, when successively transmitting the randomaccess control signals, the transmission control unit 401 controls thetarget reception power value of the random access-allocation station todecrease the target reception power value at every transmission. Inaddition, in accordance with the decrease of the target reception powerat every transmission of the random access control signal, thetransmission control unit 401 decreases the MCS level of the responsesignal as well (i.e., changes to the MCS with low transmission rate).The MCS level may be uniquely set depending on the target receptionpower value.

For example, the transmission control unit 401 applies the targetreception power setting method 1 (random access allocation) to thecalculation of the target reception power value P1 provided asnotification by the first random access control signal to betransmitted. Then, the transmission control unit 401 makes the targetreception power value P2 provided as notification by the second randomaccess control signal to be transmitted lower than the target receptionpower value P1 as the first notification by 10 dB (P2=P1−10[dB]).Preferably, this difference between the different target reception poweris determined based on the value of the allowable power difference. Forexample, the allowable power difference may be ±5 dB, and the amount ofchange of the target reception power value may be 10 dB.

As described above, the transmission control unit 401 decreases thetarget reception power value and the MCS level at every transmission inthe successive transmission of the random access control signals. Thatis, immediately after the UL MU-MIMO/OFDMA transmission procedure usingthe random access control signal in which the target reception powervalue P1 is designated, the access point 400 (transmission control unit401) performs the UL MU-MIMO/OFDMA transmission procedure using therandom access control signal with the designated target reception powervalue P2 (<P1).

As described above, even with the station 300 that could not transmitthe response signal due to the limit of the maximum transmission powerbecause of the high target reception power value in the first randomaccess control signal, the response signal can be transmitted with thetarget reception power value of the decreased reception power, which isequal to or lower than the maximum transmission power of the station300, that the second random access control signal provided asnotification.

That is, the significant decrease of the transmission opportunity of theresponse signal of the specific station 300 such as the station 300 ofthe cell edge can be prevented. In addition, since the target receptionpower value is changed based on the value of the allowable powerdifference, a station having no transmission power control function alsocan be given the transmission opportunity.

Moreover, the controlling method 1 can be applied to the control such assuppression of access of the station 300 of the cell edge using thefirst random access control signal and suppression of access of thestation 300 near the access point using the second random access controlsignal.

<Controlling Method 2>

In the controlling method 2, when successively transmitting the randomaccess control signals, the transmission control unit 401 increases theallowable power difference at every transmission. For example, thetransmission control unit 401 sets the target reception power value withthe target reception power setting method 1 (random access allocation).In addition, when the first random access control signal is transmitted,the transmission control unit 401 covers the station 300 having averagepower with a small allowable power difference. Then, when the secondrandom access control signal is transmitted, the transmission controlunit 401 can cover the station 300 that could not transmit the responsesignal with the first random access control signal by increasing theallowable power difference.

As described above, when successively transmitting the random accesscontrol signals, the transmission control unit 401 increases theallowable power difference at every transmission of the random accesscontrol signals. This increases the allowable power difference of thetarget reception power value at every transmission, and thus, even thestation 300 that could not transmit the response signal at the lasttransmission due to the limits of the maximum transmission power, theminimum transmission power, and the transmission power variable rangecan transmit the response signal at the later transmission. In otherwords, the response signal from the station 300 with a large differencebetween the target reception power value designated by the access point400 and the target reception power value based on the transmission powerthat the station 300 can transmit can be made to transmit that responsesignal easier at every transmission.

<Controlling Method 3>

In the controlling method 3, like the controlling method 1, in thesuccessive transmission of the random access control signals, thetransmission control unit 401 decreases the target reception power valueand the MCS at every transmission. Further, the transmission controlunit 401 increases a PPDU length of the UL MU transmission at everytransmission.

As described above, in the successive transmission of the random accesscontrol signals, decreasing the target reception power value and the MCSlevel at every transmission and increasing the PPDU length do not onlyachieve the similar effect as the controlling method 1 but also make theamount of information to be transmitted by the first UL response signaland the second UL response signal almost the same. That is, this cansolve the inequality between the station 300 using the first UL responsesignal for the transmission and the station 300 using the second ULresponse signal for the transmission.

In addition, controlling to decrease the target reception power valuestep by step also affects improvement of the use efficiency and thedelay property of the time resource as described below. Specifically,when the target reception power value is small, the station 300 havingenough link budget (i.e., the station 300 having extra power against thepath-loss) may also perform transmission while decreasing thetransmission power. In this case, the MCS with a speed lower than thetransmittable maximum speed is used, and the long transmission time isrequired for the same data amount. On the other hand, in thisembodiment, setting the large target reception power value at firstincreases the possibility that the station 300 capable of high-speedtransmission transmits the response signal with a high-speed MCS and ashort PPDU without unnecessarily slowing down. This can improve the useefficiency and shorten the transmission delay of the time resource.

The controlling methods 1 to 3 of the transmission control unit 401 aredescribed above.

Note that the successive transmission is not limited to be thetransmission in the TXOP section where the transmission right isobtained in advance, and a section to which the random access controlsignals are successively transmitted (a section where a flag of thecascade field is 1) in the cascade field (also called cascaded field)included in the random access control signal may be the section for thesuccessive transmission. In addition, the transmission control unit 401may perform the transmission control in the same way even when thenumber of the successive transmission is three or more.

As described above, in this embodiment, when the random access controlsignals are successively transmitted, the transmission control unit 401performs the operation to decrease the target reception power value andthe MCS level at every transmission of the successive transmission. Thiscan prevent the significant decrease of the transmission opportunity ofthe response signal of the specific station 300 such as the station 300with a low capability in controlling the transmission power.

Embodiment 4

In 11ax, two types of station classes (also called STA classes) withdifferent required accuracy such as the setting accuracy of thetransmission power and the RSSI measurement accuracy are supported. Aclass A station is a high functional station that requires that thesetting accuracy of the transmission power (absolute value) to be within±3 dB. That is, the class A station is allowed to have a setting errorof a maximum of 3 dB of the transmission power indicated by the accesspoint. On the other hand, a class B station is a low functional stationthat requires that the setting accuracy of the transmission power(absolute value) to be within ±9 dB. That is, the class B station isallowed to have a setting error of a maximum of 9 dB of the transmissionpower indicated by the access point.

As described above, in terms of whether it is possible to set thetransmission power of the station satisfying the condition that thetransmission power falls within the allowable power difference based onthe target reception power value, whether to stop the transmission ofthe signal is determined and the transmission of the response signal isstopped. This can reduce the MU interference and allow the receptionsignal to fall within the dynamic range of A/D conversion. Further, thesystem throughput can also be improved. In this embodiment, in terms ofwhether it is possible to set the transmission power of the stationsatisfying the allowance condition set based on the target receptionpower set by the access point, whether the transmission of the concernedsignal is inhibited is determined.

Thus, in this embodiment, when it is difficult to satisfy the allowancecondition due to the limits of the maximum transmission power, theminimum transmission power, and the transmission power variable range ofthe station, the reception power difference between the stations in theaccess point is reduced by inhibiting the transmission from the station.

The configuration of the station 300 is the same as that of Embodiment 2(FIG. 22 ). In addition, the configuration of the access point 400 isthe same as that of Embodiment 1 (FIG. 4 ).

Based on the target reception power value inputted from the RA controlsignal decoding unit 204 and the path-loss value inputted from thepath-loss estimating unit 207, the transmission power calculating unit205 calculates the transmission power value using Equation (3).

Based on the transmission power value inputted from the transmissionpower calculating unit 205, the information inputted from the RA controlsignal decoding unit 204 (such as the target reception power value), andthe maximum transmission power, the minimum transmission power, and thetransmission power variable range of the station 300, the transmissioncontrol unit 301 determines whether it is possible to set thetransmission power satisfying the allowance condition. Then, when it isimpossible to set the transmission power satisfying the allowancecondition, the transmission control unit 301 generates informationindicating the transmission inhibition. As described above, thetransmission control unit 301 determines whether it is possible to setthe transmission power value satisfying the allowance condition, andwhen the setting is impossible, the transmission control unit 301outputs the information indicating the transmission inhibition to theradio transmitting-receiving unit 202. Note that details of a method ofsetting the allowance condition are described later.

When the information indicating the transmission inhibition is inputtedfrom the transmission control unit 301, the radio transmitting-receivingunit 202 does not transmit the signal inputted from the transmissionsignal generating unit 210. On the other hand, when no informationindicating the transmission inhibition is inputted from the transmissioncontrol unit 301, the radio transmitting-receiving unit 202 performs thepredetermined radio transmitting processing such as D/A conversion onthe signal inputted from the transmission signal generating unit 210 andup-conversion on the carrier frequency, and then transmits the radiotransmission processed signal via the antenna 201.

Hereinafter, allowance condition setting methods 1 to 3 are describedseverally with reference to FIGS. 26A to 26C.

<Allowance Condition Setting Method 1>

FIG. 26A is an example of a method of setting the allowance condition inthe allowance condition setting method 1. In the allowance conditionsetting method 1, when the station cannot transmit the response signalwith the transmission power value that is calculated using Equation (3)due to the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation, the reception power value in the access point in a case wherethe response signal is transmitted with the actually transmittabletransmission power value is estimated in the station side. Then, even ina case where the station sets the maximum transmission power value asthe transmission power value, the transmission from the station isinhibited if the reception power estimation value in the access point islower than the lower limit value of the allowable power range, which isset based on the target reception power value. In addition, even in acase where the station sets the minimum transmission power value as thetransmission power value, the transmission from the station is inhibitedif the reception power estimation value in the access point is higherthan the upper limit value of the allowable power range. Moreover, whenthe steps of the transmission power value settable by the station aretoo rough and it is impossible to set the transmission power value toallow the reception power estimation value in the access point to fallwithin the range of the allowable power based on the target receptionpower value, the transmission from the station is inhibited. In otherwords, when there is no transmission power value settable by the stationto allow the reception power estimation value in the access point to bebetween the lower limit value and the upper limit value of the allowablepower range, the transmission from the station is inhibited. Note that amethod of setting the allowable power range is described later.

As described above, the transmission is inhibited when there is notransmission power value settable by the station to allow the receptionpower estimation value in the access point to be between the lower limitvalue and the upper limit value of the allowable power range due to thelimits of the maximum transmission power, the minimum transmissionpower, and the transmission power variable range of the station. Thisprevents increase of the reception power difference in the access point,and thus the MU interference can be reduced.

<Allowance Condition Setting Method 2>

FIG. 26B is an example of a method of setting the allowance condition inthe allowance condition setting method 2. In the allowance conditionsetting method 2, when the station cannot transmit the response signalwith the transmission power value that is calculated using Equation (3)due to the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation, the reception power value in the access point in a case wherethe response signal is transmitted with the actually transmittabletransmission power value is estimated in the station side. Then, even ina case where the station sets the minimum transmission power value asthe transmission power value, the transmission from the station isinhibited if the reception power estimation value in the access point ishigher than the upper limit value of the allowable power range, which isset based on the target reception power value. In addition, when thesteps of the transmission power value settable by the station are toorough and it is impossible to set the transmission power value to allowthe reception power estimation value in the access point to be equal toor lower than the upper limit value of the allowable power range, thetransmission from the station is inhibited. In other words, when thereis no transmission power value settable by the station to allow thereception power estimation value in the access point to be equal to orlower than the upper limit value of the allowable power range, thetransmission from the station is inhibited.

As described above, the transmission is inhibited only when there is notransmission power value settable by the station to allow the receptionpower estimation value in the access point to be equal to or lower thanthe upper limit value of the allowable power range due to the limits ofthe maximum transmission power, the minimum transmission power, and thetransmission power variable range of the station, and this makes itpossible to inhibit the transmission of a response signal having a largeeffect on the interference in the reception signal of another station.That is, inhibition of the transmission of the response signal havingthe reception power estimation value higher than the target receptionpower value in the access point above a certain degree can reduce the MUinterference. In addition, allowance of the transmission with a valuelower than the allowable power lower limit value can prevent thedecrease of the transmission opportunity of the station.

<Allowance Condition Setting Method 3>

FIG. 26C is an example of a method of setting the allowance condition inthe allowance condition setting method 3. In the allowance conditionsetting method 3, when the station cannot transmit the response signalwith the transmission power value that is calculated using Equation (3),the reception power value in the access point in a case where theresponse signal is transmitted with the actually transmittabletransmission power value is estimated in the station side. Then, even ina case where the station sets the minimum transmission power value asthe transmission power value, the transmission from the station isinhibited if the reception power estimation value in the access pointexceeds the target reception power value. In addition, when the steps ofthe transmission power value settable by the station are too rough andit is impossible to set the transmission power value to allow thereception power estimation value in the access point to be equal to orlower than the target reception power value, the transmission from thestation is inhibited. In other words, only when the reception powerestimation value in the access point exceeds the target reception powervalue provided as notification from the access point, the transmissionfrom the station is inhibited.

As described above, the transmission is inhibited only when thereception power estimation value in the access point exceeds the targetreception power value provided as notification from the access point dueto the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation. This makes it possible to restrict the transmission of theresponse signal with stricter condition than that of the allowancecondition setting method 2, and thus the MU interference can be furtherreduced. In addition, allowance of the transmission with a value lowerthan the target reception power value can further prevent the decreaseof the transmission opportunity of the station.

The allowance condition setting methods 1 to 3 in this embodiment aredescribed above.

Hereinafter, range of allowable power value setting methods 1 to 4 inthe allowance condition setting methods 1 to 3 are described severallywith reference to FIGS. 27A to 27D.

<Range of Allowable Power Value Setting Method 1>

FIG. 27A illustrates an example of a method of setting the range of theallowable power value in the range of allowable power value settingmethod 1. In the range of allowable power value setting method 1, therange of the allowable power value is changed depending on theperformance of the station (e.g., class A, class B). For example, therange width of the allowable power value of the class A station is madelarge, and the range width of the allowable power value of the class Bstation is made smaller than that of the class A station. This isbecause the setting accuracy of the transmission power of the class Astation is higher than that of the class B station.

As described above, in the station having the low station performance,the power difference between the actual reception power value in theaccess point and the target reception power value is likely to be largebecause of the reception power estimation accuracy. Thus, the rangewidth of the allowable power value is changed depending on theperformance of the station and the transmission from the station havingthe low performance is made easily inhibited, and this can reduce the MUinterference.

<Range of Allowable Power Value Setting Method 2>

FIG. 27B illustrates an example of a method of setting the range of theallowable power value in the range of allowable power value settingmethod 2. In the range of allowable power value setting method 2, therange of the allowable power value is changed depending on theallocation: the random access allocation and the specific allocation.For example, the range of the allowable power value in the specificallocation is made large, and the range of the allowable power value inthe random access allocation is made small.

In the random access allocation, since which station secures theresources from the random access is hardly determined in the accesspoint side, the resource allocation in which the scheduler takes accountof the reception power difference is impossible. Accordingly, in therandom access allocation, the interference from the adjacent RU due tothe reception power difference is likely to be greater than that in thespecific allocation. Thus, the interference due to the reception powerdifference tends to occur easily. Hence, according to this settingmethod 2, the transmission from the random access-allocation station canbe easily inhibited, and this can reduce the MU interference.

<Range of Allowable Power Value Setting Method 3>

FIG. 27C illustrates an example of a method of setting the range of theallowable power value in the range of allowable power value settingmethod 3. In the range of allowable power value setting method 3, therange of the allowable power value is changed depending on theinformation (BSS LOAD) on the number of the stations connected to theaccess point and the traffic amounts. For example, the range of theallowable power value is made large when the BSS LOAD is low, or thenumber of the stations connected to the access point is small.Meanwhile, the range of the allowable power value is made small when theBSS LOAD is high, or the number of the stations connected to the accesspoint is large. Note that the BSS LOAD is provided as notification bythe beacon.

When the BSS LOAD is high, it can be thought that the usage of theresource is high; thus, the adjacent RU is likely to be used and thesignals are likely to collide by the random access. For this, accordingto this setting method 3, the transmission from the station when thereis high BSS LOAD is made easily inhibited, and this can reduce the MUinterference.

<Range of Allowable Power Value Setting Method 4>

FIG. 27D illustrates an example of a method of setting the range of theallowable power value in the range of allowable power value settingmethod 4. In the range of allowable power value setting method 4, therange width of the allowable power value is different depending onwhether the reception power estimation value in the access point, whichis estimated based on the transmission power value that is calculatedusing Equation (3), is higher or lower than the target reception powervalue. For example, the range width of the allowable power value is madesmall when the reception power estimation value is higher than thetarget reception power value, and the range width of the allowable powervalue is made large when the reception power estimation value is lowerthan the target reception power value.

When the reception power estimation value is higher than the targetreception power value, the effect of the interference in another stationtends to be larger. For this, according to this setting method 4, thetransmission from the station that can transmit the response signal onlywith the transmission power value higher than the target reception powervalue is made easily inhibited, and this can reduce the MU interference.

The range of allowable power value setting methods 1 to 4 in thisembodiment are described above.

Note that the range of the allowable power value may be the powerdifference based on the target reception power value, or may be a rangedefined with the upper limit value and the lower limit value of therange of the allowable power value. In addition, in the above-describedallowable condition setting method 2, only the upper limit value of theallowable power value may be set.

Note that a value specified in advance or a value provided asnotification from the access point may be used as the range of theallowable power value.

Note that the range of allowable power value setting methods may be usedin combination.

Note that the allowable condition setting method and the range ofallowable power value setting method may be dynamically changed inaccordance with the signaling from the access point.

As described above, in this embodiment, the transmission control unit301 inhibits the transmission processing of the station 300 when thestation 300 cannot transmit the UL response signal with the transmissionpower satisfying the allowance condition based on the target receptionpower value provided as notification from the access point 400 due tothe transmission power control capability (performance) of the station300 such as the limits of the maximum transmission power, the minimumtransmission power, and the transmission power variable range of thestation 300. This can reduce the reception power difference between thestations 300 in the access point 400 regardless of the limits of theperformance of the station 300, or the maximum transmission power, theminimum transmission power, and the transmission power variable range ofthe station 300. Thus, according to this embodiment, it is possible toreduce the MU interference and improve the system throughput.

The embodiments of the present disclosure are described above.

Other Embodiments

-   -   (1) In each of the above-described embodiment, the configuration        is that the target reception power value is transmitted all the        time with the random access control signal; however, the        configuration may be that, depending on the A/D conversion        performance of the access point, no transmission power control        is performed, or no target reception power value is transmitted.        Whether to transmit the target reception power value may be        shifted depending on Trigger type.    -   (2) In addition, in the above described embodiments, a case        where an aspect of the present disclosure is configured with        hardware is described as an example; however, the present        disclosure can also be implemented with software cooperating        with hardware.

Moreover, in each of the above-described embodiment, a case where therandom access control signal including the random access allocation isused is described; however, it is not limited thereto, and theembodiment can be applied to a case where only the specific allocationis included. In particular, the present disclosure is useful when theaccess point cannot appropriately evaluate the path-loss and thetransmission power control capability of the station because the stateor the position of the station is changed for example.

Further, in the communication method of the present disclosure, thetransmission power (TRP) of the access point provided as notificationfrom beacon, TF, and TF-R may be power in Antenna Connector including noeffect of the antenna directivity or, when multiple antennae areprovided, may be resultant power that is the sum of power in multipleAntenna Connectors.

Furthermore, each functional block used for describing theabove-described embodiments is implemented as an LSI, which is typicallyan integrated circuit. The integrated circuit may control correspondingfunctional block used for describing the above-described embodiments andmay include an input terminal and an output terminal. The integratedcircuit may be individually formed as a single chip, or may be formed asa single chip so as to include a part or all of the functional blocks.The LSI here may also be referred to as an IC, a system LSI, a superLSI, or an ultra LSI depending on a difference in the degree ofintegration.

In addition, the technique of implementing an integrated circuit is notlimited to the LSI and may be implemented by using a dedicated circuitor a general-purpose processor. A FPGA (Field Programmable Gate Array)that can be programmed after the manufacture of the LSI or areconfigurable processor in which the connections and the settings ofcircuit cells disposed inside the LSI can be reconfigured may be used.

Moreover, if future integrated circuit technology replaces LSIs as aresult of the advancement of semiconductor technology or otherderivative technology, the functional blocks could be integrated usingthe future integrated circuit technology. Biotechnology can also beapplied.

A communication apparatus of the present disclosure includes: a targetreception power setting unit that sets at least one target receptionpower value as UL transmission power control information for controllingupstream transmission power of each of multiple stations, the targetreception power value being a target value of reception power when anupstream signal is received from each of the multiple stations; a signalgenerating unit that generates a random access control signal includingthe at least one target reception power value; and a transmitting unitthat transmits the random access control signal.

In the communication apparatus of the present disclosure, the randomaccess control signal includes a common field for providing controlinformation common to the plurality of stations as notification and astation-specific field for providing control information specific toeach of the plurality of stations as notification, and the signalgenerating unit arranges the target reception power value in thestation-specific field of the random access control signal.

In the communication apparatus of the present disclosure, the randomaccess control signal includes a common field for providing controlinformation common to the multiple stations as notification and astation-specific field for providing control information specific toeach of the multiple stations as notification, and the signal generatingunit arranges the target reception power value in the common field ofthe random access control signal.

In the communication apparatus of the present disclosure, the targetreception power value is set to a different value depending on a type ofinformation transmitted by the random access.

In the communication apparatus of the present disclosure, the targetreception power value is provided as notification in every specificallocation and random access allocation.

In the communication apparatus of the present disclosure, the signalgenerating unit arranges the target reception power value in the commonfield of the random access control signal and arranges an offset valuefrom the target reception power value in the station-specific field ofthe random access control signal.

In the communication apparatus of the present disclosure, the signalgenerating unit arranges the target reception power value in thestation-specific field for a random access-allocation station andarranges a transmission power value for transmitting the upstream signalin the station-specific field for a specific-allocation station.

In the communication apparatus of the present disclosure, the signalgenerating unit arranges the target reception power value in the commonfield for a random access-allocation station and arranges the targetreception power value in the station-specific field for aspecific-allocation station.

In the communication apparatus of the present disclosure, a transmissioncontrol unit that controls the target reception power value included inthe random access control signal when successive random access controlsignals are transmitted is further included.

In the communication apparatus of the present disclosure, the targetreception power setting unit sets a first target reception power valueand a second target reception power value, and the transmission controlunit performs UL MU-MIMO/OFDMA transmission procedure using the randomaccess control signal designating the first target reception power valueand, immediately thereafter, performs UL MU-MIMO/OFDMA transmissionprocedure using the random access control signal designating the secondtarget reception power value.

In the communication apparatus of the present disclosure, thetransmission control unit sets the second target reception power valueto a value smaller than the first target reception power value.

A communication method of the present disclosure includes: setting atleast one target reception power value as UL transmission power controlinformation for controlling upstream transmission power of each ofmultiple stations, the target reception power value being a target valueof reception power when an upstream signal is received from each of themultiple stations; generating a random access control signal includingthe at least one target reception power value; and transmitting therandom access control signal.

In the communication method of the present disclosure, the random accesscontrol signal includes a common field for providing control informationcommon to the multiple stations as notification and a station-specificfield for providing control information specific to each of the multiplestations as notification, and the target reception power value isarranged in the station-specific field of the random access controlsignal.

In the communication method of the present disclosure, the random accesscontrol signal includes a common field for providing control informationcommon to the multiple stations as notification and a station-specificfield for providing control information specific to each of the multiplestations as notification, and the target reception power value isarranged in the common field of the random access control signal.

In the communication method of the present disclosure, the targetreception power value is set to a different value depending on a type ofinformation transmitted by the random access.

In the communication method of the present disclosure, the targetreception power value is provided as notification in every specificallocation and random access allocation.

In the communication method of the present disclosure, the targetreception power value is arranged in the common field of the randomaccess control signal, and an offset value from the target receptionpower value is arranged in the station-specific field of the randomaccess control signal.

In the communication method of the present disclosure, the targetreception power value for the random access-allocation station isarranged in the station-specific field, and a transmission power valuefor transmitting the upstream signal for the specific-allocation stationis arranged in the station-specific field.

In the communication method of the present disclosure, the targetreception power value for the random access-allocation station isarranged in the common field, and the target reception power value forthe specific-allocation station is arranged in the station-specificfield.

In the communication method of the present disclosure, the targetreception power value included in the random access control signal iscontrolled when successive random access control signals aretransmitted.

In the communication method of the present disclosure, a first targetreception power value and a second target reception power value are set,and UL MU-MIMO/OFDMA transmission procedure using the random accesscontrol signal designating the first target reception power value isperformed, and, immediately thereafter, UL MU-MIMO/OFDMA transmissionprocedure using the random access control signal designating the secondtarget reception power value is performed.

In the communication method of the present disclosure, the second targetreception power value is set to a value smaller than the first targetreception power value.

An aspect of the present disclosure is useful in UL MU-MIMO/OFDMA forsolving carrier interference and a problem of the dynamic range of A/Dconversion by reducing a reception power difference between stations.

1. A communication apparatus comprising: a receiver, which, inoperation, receives a control signal including common information fieldfor one or more terminal stations including the communication apparatusand one or more user information fields, each of the one or more userinformation fields corresponding to one of the one or more terminalstations, wherein the control signal is a trigger frame that solicitstransmission of an uplink (UL) response frame from each of the one ormore terminal stations, and each of the user information fields includesa modulation and coding scheme (MCS) field and a target reception powerfield for the UL response frame transmitted from one of the one or moreterminal stations; circuitry, which, in operation, determines a transmitpower of the transmission of the UL response frame based on a value ofthe target reception power field and a value of the MCS field includedin the user information field corresponding to the communicationapparatus; and a transmitter, which, in operation, transmits the ULresponse frame based on the determined transmit power.
 2. Thecommunication apparatus according to claim 1, wherein each of the userinformation fields includes the target reception power field that isindividually set for one of the one or more terminal stations, and thevalue of the target reception power field is used to control a transmitpower of the transmission of the UL response frame from one of the oneor more terminal stations.
 3. The communication apparatus according toclaim 2, wherein the control signal includes transmission prohibitioninformation instructing each of the one or more terminal stations thatthe transmission of the UL response frame is not permitted when thetransmit power of the UL response frame cannot be set within apermissible power range for each of the one or more terminal stations.4. The communication apparatus according to claim 1, wherein each of theuser information fields includes an ID of one of the one or moreterminal stations, and the value of the target reception power field isassociated with the ID.
 5. The communication apparatus according toclaim 1, wherein the value of the target reception power field isindicated by an offset value to be added to a determined value.
 6. Thecommunication apparatus according to claim 5, wherein the offset valueis generated based on a quantized value, and a number of bits of theoffset value of the target reception power field is smaller than anumber of bits corresponding to a non-quantized value of the targetreception power field.
 7. The communication apparatus according to claim1, wherein the control signal is a random access control signal.
 8. Thecommunication apparatus according to claim 1, wherein the control signalis a random access control signal, and the value of the target receptionpower field included in the random access control signal is controlledwhen the random access control signal is continuously transmitted. 9.The communication apparatus according to claim 8, wherein a first valueand a second value are set in one or more target reception power fields,and UL MU-MIMO/OFDMA transmission using the random access control signalthat includes the second value as a target reception power value takesplace after UL MU-MIMO/OFDMA transmission using the random accesscontrol signal that includes the first value as a target reception powervalue.
 10. The communication apparatus according to claim 9, wherein thesecond value is smaller than the first value.
 11. The communicationapparatus according to claim 1, wherein each of the user informationfields includes an allocation information field of a resource unit forone of the one or more terminal stations.
 12. The communicationapparatus according to claim 11, wherein each of the user informationfields includes an ID of one of the one or more terminal stations, andthe ID indicates which terminal station the resource unit is allocatedto.
 13. The communication apparatus according to claim 11, wherein eachof the user information fields includes an ID of one of the one or moreterminal stations, and the ID indicates that the resource unit isallocated for random access.
 14. The communication apparatus accordingto claim 13, wherein the ID indicates that the resource unit isallocated for random access by the one or more terminal stations. 15.The communication apparatus according to claim 1, wherein the circuitry,in operation, determines the transmit power of the transmission of theUL response frame based on a capability of communication apparatus. 16.The communication apparatus according to claim 1, wherein the circuitry,in operation, determines the transmit power of the transmission of theUL response frame based on a maximum transmit power of the communicationapparatus.
 17. A communication method for a communication apparatus, thecommunication method comprising: receiving a control signal includingcommon information field for one or more terminal stations including thecommunication apparatus and one or more user information fields, each ofthe one or more user information fields corresponding to one of the oneor more terminal stations, wherein the control signal is a trigger framethat solicits transmission of an uplink (UL) response frame from each ofthe one or more terminal stations, and each of the user informationfields includes a modulation and coding scheme (MCS) field and a targetreception power field for the UL response frame transmitted from one ofthe one or more terminal stations; determining a transmit power of thetransmission of the UL response frame based on a value of the targetreception power field and a value of the MCS field included in the userinformation field corresponding to the communication apparatus; andtransmitting the UL response frame based on the determined transmitpower.